The cost of solar modules has fallen substantially over the past six months and is expected to fall still further. Photovoltaic solar energy is nearing its breakthrough point. This will happen once the cost of solar electricity equals the cost of electricity from the grid.
That point is referred to as "grid parity" and will vary from country to country depending on the market segment. In sunny California, the grid parity point for private households is near, as solar irradiation is high and consumers pay a high price for their electricity. In France– a little less sunny and with low electricity costs due to its cheaply available nuclear power– grid parity is a little further away.
Nevertheless, grid parity for solar PV will come to all countries eventually, because the cost of solar electricity will continue to fall, while the cost of electricity generated through fossil fuels will only increase. Solar modules and systems will become cheaper as a result of improvements in technology and the scaling up of manufacturing processes. The cost of electricity from the grid will become more expensive as a result of growing demand and the scarcity of fossil fuels. Increasing environmental concerns translating themselves into eco-taxes may raise the price as well. Grid parity could be reached in California and southern Italy in less than two years, while it may take a little longer in other countries, such as Spain, Portugal, and Greece. Other countries will soon follow suit. What can we then expect?
Once grid parity has been reached, consumers will be presented with a choice: (1) to buy all their electricity from traditional energy utilities or (2) to pay the same price and (partly) generate green renewable solar energy from their own roofs. Not only will the growing focus on green and sustainable development make solar power a preferential alternative, but even more important will be price stability. Following its installation, a solar energy power system will generate solar electricity at fixed cost for at least 25 years. Operation and maintenance costs are negligible. The cost of solar electricity will be determined by the depreciation schedule and the interest rate. Both of these can be forecast over a long period of time. Compare this to the annually changing cost of grid electricity. Is it likely that fossil fuel-based electricity prices will be stable over the next 25 years? This would seem to be an unlikely scenario when looking at growing concerns about climate change, Asia’s rapidly increasing energy demands, international political instability, and anticipated uncertainties about the easy exploration of oil reserves.
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Showing posts with label Solar Energy. Show all posts
Showing posts with label Solar Energy. Show all posts
The Solar Energy Breakthrough Will Change the Energy Business Landscape
Payback of Solar Energy Systems
A customer investing in a solar PV system should understand the economic payback on his or her investment, even if there may be strong non-economic (e.g. environmental) factors driving the purchasing decision.
The initial investment depends on the system size. A convenient factor that takes this into account is the price per peak Watt (Wp) of the system. Hence, a 2000 Watt peak (2kWp) solar energy system costing $16000 in total (i.e. including installation) will correspond to a price of $8/Wp. In some countries, you may be able to obtain a grant or rebate towards the cost of the system, which will obviously improve the economic payback on the purchase.
You may have different options to finance the purchase, but each of them has a cost. If you are investing cash then you lose its future interest; if you borrow the money then you pay a financing cost. Either way, there is a cost of financing the purchase that can be represented by a so-called "discount rate". The normal cost of borrowing may be reduced if local banks offer low interest loans for the purc
hase of solar PV systems. Alternatively, your bank might allow you to extend your home loan or mortgage; this may be the cheapest form of standard borrowing.
The economic return on your investment is the value of the electricity that you generate. This will, as a minimum, displace electricity that you would have otherwise bought from your utility or energy service provider during the day. Through certain schemes, it may be separately metered and rewarded at a defined rate (possibly related to the domestic tariff or set by a national or state program). Market incentive programs in certain countries offer some or all of the range of benefits from grants or rebates and low-interest loans to preferential electricity purchase rates. Your local Retailer (also known as "dealer") should be able to advise if any incentives are available to you.
The following graph shows the impact of the solar system price on the payback time of the purchase as a function of the value of the electricity generated, using a discount rate of 5%. As you would expect: the cheaper the Solar System, the faster the economic payback. The higher your regular electricity rate (shown on the bottom axis), the faster the payback on your Solar Energy System.
For example, if your average electricity rate is 20 US cents per kilowatt hour and your installed cost was $4 per Watt (this is achievable where government or utility programs are available), your payback time will be just over 15 years. If you are exposed to peak pricing on electricity rates, take account of tax incentives (available for Corporate purchasers), payback closer to 10 years is reasonable.
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Solar Energy Businesses in the World
Here you can find solar energy business oppurtunities throughout the world..
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5 Powerful Reasons To Invest Into Solar Panels and Save Money!
Save Money With Solar Panels
So 2008 is winding down and many things have happened this year. Recently the particle accelerator (Large Hadron Collider) was fired up and Barack Obama made young people everywhere have faith in politics.But the real theme of 2008 has been gas prices. Many people everywhere are still wondering whether gas prices are going to get any cheaper. The reality is that, it will never get cheaper. That's right - never. Not only will gas never get cheaper, but everything we pay for that relies on petrochemicals for production - that is - everything you use - from your chair, computer, desk, plastics, vehicles - will never get cheaper.
Just think about that for a moment - everything that you rely on takes a source of energy that is quickly depleting. It takes many different refined sources of oil (petrochemicals) to manufacture pretty much all the goods and technology we enjoy in abundance. Some argue we have 20 years left, some argue we have 50 - the bottom line is there is a time line within most of our lifetimes.
Let's take a look at your home or apartment for a moment.
Depending on your location, your home is tied into a vast energy grid that is powered by things such as Hydroelectric dams to coal power plants. All of these take petrochemicals to maintain and construct as well.
My main point here is that, as a globe we need to begin changing our energy infrastructure while we have the oil to do it. Don't sweat though, the power is actually in your hands. So while we have this black gold available, we're still able to manufacture such things as solar panels to empower people to get off the grid.
Solar panels are pretty new, but have been around in theory for many many years. If you're a home owner, or even live in a small apartment - a solar panel can help you save money in the long run. But why should you invest besides reasons such as a lack of oil resources?
Here's 5 reasons why you should:
Reason #1 - Durability & Longevity
On average, a solar panel can last up to 30 years or more. With just a few arrays set up, you can be powering your home with your own renewable energy. Not only that, but solar panels are designed to withstand harsh climates. One common misconception is that you need the sun shining to convert to electricity. Solar panels can still convert from solar energy to electrical or thermal power even on a cloudy day (although not at the same capacity).
Reason #2 - Unlimited Power!
While everyone else is crying and whining about gas prices and high energy costs - you will have an unlimited supply of solar power. Unless the sun blows up and destroys our entire solar system - you won't really need to worry about never having power
.Reason #3 - Tax Incentives
Once you invest into solar, you are eligible for Federal, State, Provincial And Utility Tax incentives and rebates. These aren't the '$30 off' from your coffee maker rebates - they add up big time! For example, in Australia, if you spend $16,000 on a solar set up, they will rebate you up to $8000 back. This doesn't include other rebates you can get either. You'll need to check your own country's government policies - but, in the next 5-10 years - all countries will be jumping on the solar bandwagon.
Reason #4 - Not Just A 'One Time' Set Up + Easy Installation
With solar, you don't need to invest into a bunch of costly arrays right away. You're able to set up one panel at a time, and add additional panels whenever you feel the time is right. Furthermore, installing a solar panel is actually quite a lot easier than people think. You can do it yourself, or have an installer come and have it set up for you the same day.
Reason #5 - Add A 'Capacitor' And You Are Laughing + No More 'Blackouts'
A capacitor is a device that lets you store unused energy. So if you're over producing solar energy - usually two things happen. You can either give that energy back into the system grid (that is, pooling your energy into the grid for other people in your community to use) or you can store it in a capacitor. If you were ever to run out of energy, or you are seeing 'under production' - a capacitor lets you have energy that you stored previously. This means you will always have a back up of energy in a time of crisis.
What this also means (and having solar in general) is that when the system grid goes over its maximum energy potential (that is, too much energy is being used in the city which causes a blackout) - you will still be powered up! Your neighbors will be looking in jealousy at the one shiny house in the block.
So there you have it. If you're still not convinced - check out http://solar.envirohub.net for more information.
Ethiopia powers up with solar energy
Germany's Solar Energy Foundation aims to improve living conditions and foster a solar industry in Ethiopia.
The rural village of Rema in Ethiopia could become a cleantech boom-town if the work of Germany's Solar Energy Foundation continues its success in the region.
Since 2006, the foundation has installed 2,000 solar systems in Rema and in nearby Rema ena Dire, the biggest solar power project in East Africa. The project has brought power to 5,500 residents in a country where only one percent of people in rural areas have access to electricity.
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Rising Oil Prices Vs Solar Energy
Rapidly rising oil prices have led to such a demand for solar energy that the industry could operate itself without subsidies in just a few years, according to industry leaders.
At the Munich solar industry trade fair, industry leaders were increasingly confident that grid parity - where electricity from the sun can be produced as cheaply as it can be bought from the grid - is now just a few years away.
Solar photovoltaics (PV), which convert sunlight into electrical power, have long been dismissed as too expensive and not efficient enough to make a meaningful contribution to the battle against climate change.
But costs are falling dramatically as PV production escalates as electricity prices rise rapidly year on year in line with soaring oil and gas prices.
Germany now has nearly half a million houses fitted with PV panels. The feed-in tariff pays people with solar panels above-market rates for selling power back to the grid. Governments around the world might well take notice of the German approach.
With high oil prices have boosting demand even more. The market will probably expand another 40% this year, according to the German solar industry association.
Previous predictions that grid parity would be reached in Germany in 5-7 years, now look very conservative since. Germanys predictions allowed for only a 3% rise in electricity prices each year. In many countries increases of 20% a year are becoming the norm.
The China-based Suntech, the world's biggest maker of PV panels, plans to double production this year.
They believe grid parity in Germany can be reached within 5 years. In California and Italy, where there is lots of sun and high electricity prices, they said grid parity for PV systems had already been achieved.
And the great thing about solar energy is that although you have an upfront cost, the fuel is free and is not controlled by another country.
PV costs are falling rapidly and will continue to do so as the efficiency of panels improve and installation costs drop. Moreover, the price of silicon - which can be 70% of panel costs - is also likely to fall as new production technology becomes available.
Oil Freedom through Solar Energy
- A massive switch from coal, oil, natural gas and nuclear power plants to solar power plants could supply 69 percent of the
- A vast area of photovoltaic cells would have to be erected in the Southwest. Excess daytime energy would be stored as compressed air in underground caverns to be tapped during nighttime hours.
- Large solar concentrator power plants would be built as well.
- A new direct-current power transmission backbone would deliver solar electricity across the country.
- But $420 billion in subsidies from 2011 to 2050 would be required to fund the infrastructure and make it cost-competitive. {That is equivalent to 1 year of military expenditures}
High prices for gasoline and home heating oil are here to stay. The
Well-meaning scientists, engineers, economists and politicians have proposed various steps that could slightly reduce fossil-fuel use and emissions. These steps are not enough. The
Solar energy’s potential is off the chart. The energy in sunlight striking the earth for 40 minutes is equivalent to global energy consumption for a year. The
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Cool Ideas - Solar Energy
Global Warming is a big issue but the world currently needs oil to run. This can be chnaged if governments and people were willing to switch to alternative methods of energy production such as Solar Energy.
Our Future Energy - Solar
Great video.. Wow! I didn't know that burning fossil fuels produced pollution!
Capturing and Storing Energy From the Sun
Current interest in solar energy is not the first time people have been excited about its potential. Reportedly, the first flat-plate collector appeared in 1774. It consisted of a wooden box with three layers of glass that heated air to 140° F. By the turn of this century, development had progressed to the point that efficiencies were about as good as they are today.
Other sources of energy were more economical and convenient to use, so there was little incentive to put solar energy to work. But the finite supply of fossil fuels is now recognized, and we must prepare for the time when their cost may be much higher. An added benefit of solar energy would be reduced pollution, which will become more important as population increases.
The first consideration for any application is to reduce the energy requirement to the point where the economics of using solar collecting equipment is more favorable than investing in energy conservation measures. Most homes were constructed when fuel was plentiful and extremely cheap, so investment in solar heating and cooling should be thought about only after adequate weatherization.
The real cost of energy delivered from solar systems may range from the equivalent of $1 up to $10 per gallon of propane. At these levels, many energy conserving improvements will be economical. There is another payoff for weatherizing homes: they will be more comfortable because cold drafty conditions are reduced.
Equipment Can Prove Expensive
Energy from the sun is free, but equipment for collection, storage, and use can be expensive. A number of factors are involved in determining how much can be invested for a solar collecting system but the first cost of the equipment and the amount of energy that can be effectively used during its practical life are most important. The energy that can be used is determined by the solar energy available, ability of the collector to deliver energy, and whether that energy can be put to work or stored at the time it is collected.
An application such as water heating requires energy on a regular basis throughout most of the year, so more money can be invested in reliable, efficient hardware. Grain drying requires very large amounts of low-quality energy during a short period of time, so the system must be inexpensive or used for other applications during the rest of the year.
Investing in a solar collector depends to a great extent on tax credits granted by a State. With limitations, the Federal income tax credit of 25 percent plus the State tax credit in some States will now pay for up to 55 to 75 percent of the investment in solar equipment — which makes many solar systems economical.
Solar energy collecting systems often are classified as either active or passive. In active systems a fan or pump moves the working fluid or air through the collector. The fan or pump is turned on or off depending on whether the working fluid temperature is high enough to provide heat for storage or a process.
In passive systems the working fluid moves because of difference in density (hot air or hot water moves up and cold air or cold water moves down) or where the energy is moved by radiation or conduction heat transfer. Passive systems sometimes are defined as those where only a small amount of energy from fossil origin is used for moving the collected energy, for example one unit from fossil origin to 50 units derived from solar.
A system that combines both active and passive features is sometimes called a hybrid system and some authors classify this as a third type.
Photovoltaic collectors convert sunlight into direct current electrical energy but that method of energy collection is very expensive and used only for special purposes such as providing a small amount of energy for remote communications equipment and powering space vehicles. Therefore, this discussion is limited to applications where the function is to convert solar energy into heat energy.
Active Systems
Focusing collectors and flat-plate collectors are used for heating applications. Focusing collectors have a large area for entry of solar radiation that is then reflected onto a receiver. The entry area must be positioned so it sees the sun. This requires some type of mechanism to move the collector assembly during the day, which increases the cost of the collector.
High temperatures can be attained by focusing collectors. But most applications for heat in residences and farm service buildings can make use of energy gathered with flat-plate collectors.
Many different types of flat-plate collectors are being used or under development for putting solar energy to work in homes, farm service buildings, and agricultural processes. They range from simple systems costing very little to incorporate in the design of a new building, to more expensive equipment where cost is so high that the system would be economical only if conventional energy expenses increase.
Examples of inexpensive, simple systems are transparent roofs on farm service buildings for heating air to dry grain, or south-facing windows on residences that allow solar energy to be trapped inside. Complete systems for heating water may have an installed cost of $50 or more per square foot of collecting area.
Active systems are generally regarded as more complicated than passive systems, but a process such as grain drying can use a simple collector and maybe only one thermostat. Besides, passive systems can become complicated when controls and equipment are used to restrict natural air movement or when movable insulation is incorporated into the design. The prospective user should keep in mind that it is best to use as simple a system as possible that will provide heat for the user's needs.
Flat-plate collectors may be designed for operating only a few degrees above the outside temperature for uses such as grain drying. Those required to provide heat to a residence during winter may be designed for operating at a temperature differential of 100° F or more. Generally, cost of a flat-plate collector rises as the operating temperature differential increases.
The typical active system consists of a collector assembly, an energy storage unit, a control system, and two energy transport systems — one between the collector and storage and another between the storage and the process requiring heat.
Some vendors provide complete systems while others offer components that can be used to make up a complete system. Choosing between them depends on the type of process involved and abilities of the individual or contractor installing the system. Competent assistance should be found When planning a components system, because each component must be sized correctly to work with other parts of the system.
Backup System Needed
A backup heating system is needed because there are cloudy periods when solar energy cannot provide the necessary heat. The control system is quite important because it must be able to sense when heat can be added to storage, removed from storage, or when the backup furnace is required.
All these functions must work automatically because the typical user will not be present or may not be inclined to provide the manual controls needed to make the system work effectively.
The flat-plate collector for an active system consists of one or more of the following: 1) An absorber plate 2) A transparent cover or covers 3) Insulation behind the absorber plate 4) A box to contain the parts 5) An inlet and outlet to let the working fluid pass. The working fluid can be either liquid or air.
The bare-plate collector is used where low temperature differentials are adequate. Adding a transparent cover above the absorber allows a higher temperature to be maintained because heat loss from the absorber is reduced. A second transparent cover can be added to obtain even higher temperatures.
The absorber plate is generally made of sheet metal, or a flat surface of other material, and painted black to absorb the sun's rays. Flat black paint used for absorbers in high temperature collectors should be capable of operating at temperatures to 300° F, and possibly higher, without damage.
The absorber plate must serve to transfer absorbed solar heat to the working fluid. Fins protruding into the air may be added to the absorber, giving more surface area to transfer heat. With the liquid-type collector, the distance between liquid tubes determines how well heat can be transferred.
The weight of material in an absorber plate influences the time it takes to heat up before the working fluid can be circulated. Heavy plates require more time to heat up than light plates. During intermittent cloudiness, the plate might not heat up before a cloud cuts off solar energy. Then the heated plate would cool down while waiting for another period of sunshine.
Insulation Important
An exposed hot surface quickly loses heat, so the back side of the absorber must be insulated. Insulation between the absorber and the back of the collector box should be stable at high temperatures. Some insulations have organic materials in them that break down at high temperatures.
Vapor may deposit particulate matter on the inside of the transparent cover. This could make the collector useless until a new transparent cover is installed.
Features to reduce heat loss from the sides and ends of the collector should be incorporated into the box for the absorber plate. Collector boxes need to be sealed to exclude water, and strong enough to resist the loads imposed on them by wind and snow. Pipes or ducts entering or leaving the collector box should be insulated to reduce heat loss.
Glass has been commonly used as a transparent cover for collectors, but some plastics have desirable characteristics. Low-iron and plate glass are recommended because they absorb less solar energy than ordinary glass. The glass surface can be treated to reduce reflection, increasing transmitted energy.
Plastics are being used in many applications because construction of frames is not so critical and most plastics are somewhat less expensive than glass. Plastics resist impact stresses better than glass and generally transmit as much or more solar radiation. However, plastics generally allow more thermal energy loss than glass.
Care should be taken in selection to get plastic resistant to ultraviolet rays in sunlight and to the high temperatures encountered. The plastic should not retain a static charge which would attract dust.
Fans or pumps for moving the working fluid between the collector and storage need to be capable of long term, efficient operation. Ducts and pipes should be sealed and insulated; the amount of insulation recommended depends on the temperature difference between the working fluid and the surrounding air. Liquid leaks in pipes can be easy to spot, but air leaks in ducts present a problem because they aren't easily detected.
The control system needs to make decisions for operation of components and to be as simple as possible but still adequate to control all the aspects of operation. Where possible, users should understand the system so as to recognize when service is required or make their own adjustments and repairs.
Passive Systems
Passive solar systems are generally simple and low in cost for the quantity of heat added. Most are operated with a minimum of controls designed into the system, but may require manual adjustment.
Careful design may be required to obtain reasonably stable temperatures in the environmental space. Overheating or very cool conditions can result if the right combination of glazing and storage are not provided.
The four main types of passive solar systems are direct gain, thermal storage wall, attached sun space, and convective loop.
The direct gain system uses south-facing transparent walls, or windows, that allow solar radiation to enter directly into the environmental space that is to be heated. A part of the solar radiation is absorbed by the floor and a part reflected onto the walls and ceiling where it is absorbed.
The absorbed radiation is converted to thermal energy (heat). Some of it goes to heat up the storage material and some is lost by convection to the air which comes in contact with the floor and walls.
Movable insulation to reduce heat loss through the transparent cover at night increases overall thermal performance of this system.
The direct gain system is effective for south-facing surfaces because of the sun's low position in the sky during winter months. In summer when the sun is at a higher position in the sky, the glazed area can be shaded by overhang on the structure, awnings, or deciduous trees.
Advantages of the direct gain system are that it is one of the least expensive, simplest solar systems and can function without constructing a storage component in cases where the floor or wall can be used.
Disadvantages are degradation of fabrics and other materials in the room by ultraviolet radiation in the sunlight, temperature swings in the room which can be quite high unless thermal storage is carefully designed, the need for movable insulation to reduce heat loss through the glazing at night, and too much glare which can occur in the room during the day.
Thermal Siphon
The convective loop system has an absorbing surface placed behind the transparent cover on the south wall. This surface converts the sun's rays to heat energy that heats up the air and causes a thermal siphon effect. Cool air from the room flows up past the absorber where it is heated, and then exhausts near the ceiling. A small collector can be effective at heating a room during daytime, but there is limited storage and the room will cool off quickly at night.
Air movement caused by the thermosiphon would not be very effective at adding heat to massive walls inside the room. Thus one must be careful not to have too large a collector. At night, reverse thermal circulation can occur since the cold glass near the absorber cools it and will cause cool air to exist in the space between them which sets up a reverse circulation process. This should be prevented by closing off the loop at night.
Advantages of the convective loop system are that glare and ultraviolet degradation of fabrics are not problems, it is relatively inexpensive, it can be readily added to existing buildings, and night heat losses can be lower for other types of passive design. Disadvantages are that careful engineering and construction are required to insure proper airflow, prevent overheating, and assure adequate thermal isolation at night.
The thermal storage wall typically is a masonry wall with the south-facing side painted black to absorb solar radiation. The wall has one or two transparent covers. During the day, the south face of the wall is heated and starts the process of conducting heat through the wall. A so-called temperature wave moves through the concrete, causing the inside surface to be the wannest a few hours after sundown.
With thermal storage walls, glare and ultraviolet degradation of fabrics is not a problem, the temperature swing in adjacent living space is much lower, and designs are becoming available for allowing the proper sizing of units for homes. Disadvantages are the increased cost of constructing the wall, the space it occupies, and the amount of heat lost to the outside at night unless movable insulation is used.
Greenhouses, or similar structures called attached sunspaces, can be attached to new or existing buildings. The greenhouse is heated during the day and this warm air can be added to adjacent living space to reduce heat requirements.
A massive thermal storage wall can be used to absorb some of the solar radiation directly and transmit it to the adjacent living space and greenhouse during nighttime hours. The wall can reduce the amount of overheating that occurs in the greenhouse during daytime.
The sunspace acts as a buffer zone to reduce heat loss at night from the building to the outdoors. Advantages of the attached sunspace are that it provides smaller temperature swings in adjacent living space, reduces heat loss from adjacent living space to the outside, and is readily adaptable to existing buildings. Disadvantages are that thermal performance varies greatly from one design to another, making performance difficult to predict, and cost can be quite high if commercial buildings are used.
Storage Systems
Solar energy is received during the day and some type of storage system is required to allow that heat to be available at night. The two basic mechanisms for storing energy are to use sensible heat capacity of materials and to use the latent heat of fusion (heat given up during a change in phase from liquid to solid states).
Sensible heat capacity of a material is the amount of energy it takes to heat a unit of material. For example, it takes 1 British thermal unit (Btu) of energy to increase the temperature of 1 pound of water by 1° F. It takes about 5 pounds of rocks or concrete to store as much energy as 1 pound of water.
Even though water has the highest sensible heat storage capacity, rocks and concrete have advantages in applications such as air-type collectors and passive solar applications. Data in the table show the quantity of rocks or water required to store 500.000 Btu's of energy. This amount of energy would be equivalent to the heat produced by burning 7 to 8 gallons of propane.
| Thermal energy storage properties and requirements to store 500,000 Btu's with a 30° F change in temperature. | |||
| Rocks | Water | Phase-change material | |
| Specific heat capacity, Btu per lb per degree F | 0.2 | 1.0 | 0.5 (ave.) |
| Heat of fushion, Btu's per lb | - | - | 100 (ave.) |
| Density. lbs per cu ft | 90 | 62 | 100 |
| Storage of 500,000 Btu's | |||
| Weight, lbs | 88,500 | 16,670 | 4,350 |
| Volume, cu ft | 930 | 2701 | 552 |
| 12,000 gallons. | |||
| 2An additional 25% for passage of air is added to volume. | |||
Density of a material is the weight of that material that can be put in a box which is 1 foot in all three dimensions.
Multiplying the specific heat capacity by the density gives the volumetric heat capacity of a material. The volumetric heat capacity of water would be 62 while that for rocks would be 18 Btu's per cubic foot per degree Fahrenheit of temperature change. Thus water has a volumetric heat capacity over three times as great as for rocks.
Materials that change from liquid to solid at a temperature of around 90° F are being developed for the phase-change process, because large quantities of energy can be stored in a relatively small space. When water changes from liquid to solid (forms ice), 144 Btu's per pound of heat (the latent heat for fusion) are given up. Obviously, water cannot be used as a phase-change material in solar heating applications because 32° F is much too low to provide comfort.
Glauber's salt — sodium sulfate decahydrate — melts and freezes at 90° F and is one material being used for phase-change storages.
Considerable work is being done on these phase-change materials because large quantities of heat can be stored in a small space.
Phase-change material properties shown in the table are characteristic of those being used or considered for applications with solar systems. It takes four times the weight and five times the volume for water to store the same quantity of heat as this typical phase-change material. That has obvious advantages for retrofit applications because much less space is required to provide heat storage.
Rocks, Water Are Common Materials
Most energy storage systems that have been installed to date use the specific heat capacity of materials for storage. Rocks and water are both common materials and storage structures can be purchased or easily built.
An insulated steel tank is commonly used for liquid storage systems. Underground concrete tanks have been used for some larger systems, and fiber glass tanks for a number of smaller ones. Materials used to construct the tanks should be compatible with any chemical treatment the water requires.
Designs of a storage tank for water should allow for temperature stratification in the tank. This means hot water can be added to or removed from the top of the tank, and cold water can be added or removed from the bottom.
The void space between rocks in a storage allows passage of air. The rocks must be small enough so there is adequate surface area to allow heat transfer from the working fluid, air, to the rocks but large enough so the passageways allow easy movement of the working fluid. Rocks with an average diameter of 1 to 2 inches are usually recommended.
Rocks and packaged, phase-change materials are commonly used for air-type collectors. Packages for phase-change materials must be designed so there is adequate surface area for transfer of energy into or out of the unit.
All heat storage units — liquid, solid, or phase-change — must be insulated whether in the building, outside, or underground.
Reflectors
Reflecting surfaces can be positioned so they increase the amount of solar energy arriving at a collector. The correct position for a reflector depends on orientation of the collector and the season of the year during which it will be used. No general rule of thumb can be used to estimate the increase in collected energy because the changing position of the sun with the seasons affects the direction where solar energy is reflected.
The increase in collected solar energy per dollar invested in a reflector should be greater than from additional investment in collectors.
A computer simulation has been used to predict the increase in energy collected by a south-wall solar collector installed on a farrowing house in Kansas. A white-painted reflector in front of the collector and extending out as far as the collector is high (8 feet) increases collected solar energy by 15 to 16 percent. However, not all the reflected energy can be effectively used during spring and fall, so the net increase is only about 12 percent. Experimental testing has shown the computer simulation approximately correct for this Kansas location.
Information Sources
The prospective user should spend some time learning about solar energy technology. Another method is to enlist a good consultant, but the number of experienced technical personnel is limited and most are quite busy.
Sources for further study are textbooks and publications from State and Federal agencies, industrial associations, and companies selling components or complete systems. The National Solar Heating and Cooling Information Center, P.O. Box 1607, Rockville, MD 20850 provides a broad range of general information about solar energy.
Most State energy offices have personnel assigned to provide assistance on solar energy that is applicable to local conditions. They would be helpful in locating engineers and architects.
The Cooperative Extension Service provides publications and educational programs for agricultural applications. They will have plans available as they are developed.
Source: http://www.healthguidance.org/authors/488/Bob-BerglandNew Ways to Store Solar Energy for Nighttime and Cloudy Days
Solar power, the holy grail of renewable energy, has always faced the problem of how to store the energy captured from the sun’s rays so that demand for electricity can be met at night or whenever the sun is not shining.
The difficulty is that electricity is hard to store. Batteries are not up to efficiently storing energy on a large scale. A different approach being tried by the solar power industry could eliminate the problem.
The idea is to capture the sun’s heat. Heat, unlike electric current, is something that industry knows how to store cost-effectively. For example, a coffee thermos and a laptop computer’s battery store about the same amount of energy, said John S. O’Donnell, executive vice president of a company in the solar thermal business, Ausra. The thermos costs about $5 and the laptop battery $150, he said, and “that’s why solar thermal is going to be the dominant form.”
Solar thermal systems are built to gather heat from the sun, boil water into steam, spin a turbine and make power, as existing solar thermal power plants do — but not immediately. The heat would be stored for hours or even days, like water behind a dam.
A plant that could store its output could pick the time to sell the production based on expected price, as wheat farmers and cattle ranchers do. Ausra, of Palo Alto, Calif., is making components for plants to which thermal storage could be added, if the cost were justified by higher prices after sunset or for production that could be realistically promised even if the weather forecast was iffy. Ausra uses Fresnel lenses, which have a short focal length but focus light intensely, to heat miles of black-painted pipe with a fluid inside.
A competitor a step behind in signing contracts, but with major corporate backing, plans a slightly different technique in which adding storage seems almost trivial. It is a “power tower,” a little bit like a water tank on stilts surrounded by hundreds of mirrors that tilt on two axes, one to follow the sun across the sky in the course of the day and the other in the course of the year. In the tower and in a tank below are tens of thousands of gallons of molten salt that can be heated to very high temperatures and not reach high pressure.
“You take the energy the sun is putting into the earth that day, store it and capture it, put it into the reservoir, and use it on demand,” said Terry Murphy, president and chief executive of SolarReserve, a company backed in part by United Technologies, the Hartford conglomerate.
Power plants are typically designed with a heat production system matched to their electric generators. Mr. Murphy sees no reason why his should. His design is for a power tower that can supply 540 megawatts of heat. At the high temperatures it could achieve, that would produce 250 megawatts of electricity, enough to run a fair-size city.
It might make more sense to produce a smaller quantity and run well into the evening or around the clock or for several days when it is cloudy, he said.
At Black & Veatch, a builder of power plants, Larry Stoddard, the manager of renewable energy consulting, said that with a molten salt design, “your turbine is totally buffered from the vagaries of the sun.” By contrast, “if I’ve got a 50 megawatt photovoltaic plant, covering 300 acres or so, and a large cloud comes over, I lose 50 megawatts in something like 100 to 120 seconds,” he said, adding, “That strikes fear into the hearts of utility dispatchers.”
Thermal storage using molten salt can work in a system like Ausra’s, with miles of piping, but if the salt is spread out through a serpentine pipe, rather than held in a heavily insulated tank, it has to be kept warm at night so it does not solidify, among other complications.
A tower design could also allow for operation at higher latitudes or places with less sun. Designers could simply put in bigger fields of mirrors, proponents say. A small start-up, eSolar, is pursuing that design, backed by Google, which has announced a program to try to make renewable electricity for less than the price of coal-fired power.
Mr. Murphy helped build a power tower at a plant in Barstow, Calif., sponsored by the Energy Department in the late ’90s. It ran well, he said, but natural gas, a competing fuel, collapsed in price, and the state had few requirements for renewable power.
“There were not renewable portfolio standards,” Mr. Murphy said. “Nobody cared about global warming, and we weren’t killing people in Iraq.”
How to Store Solar Energy
If you’ve ever wondered how to store solar energy here are the basics. Solar energy is energy from the sun which is collected here on earth for heating, lighting and other human needs. Many of our basic energy needs can be addressed by using solar power. This can be done directly or indirectly but is not easy to do on a large scale. To store solar energy two components are required.
A means of collecting the solar energy and a way to generate it are needed to make sure we can access the sun’s energy. The collector collects the sun’s radiation and converts some of it to another form of energy such as electricity and heat. It is critical to find a way to store solar energy. This is because the sun does not shine for 24 hours a day and on overcast days the energy is inhibited.
The storage equipment is a way to accumulate excess energy when the sun’s rays are at maximum strength. When the sun is not shining or obscured this stored energy can be used. A backup supply also forms part of this system for times when the stored energy is insufficient. There are many ways to store solar energy. Three types of collectors are used to collect the sun’s radiation: 1) flat-plate collectors, 2) focusing collectors and 3) passive collectors.
Solar energy is very well suited for heating purposes. This heat energy can be stored in a liquid like water or a packed bed. A packed bed is a container in which small objects like stones can be placed. The stones are able to store solar energy. Heat energy can also be stored in phase-changer or heat-of-fusion units which use chemicals to alter solid to liquid at certain temperatures. Later the liquid can return to its solid form and the energy can be used.
This process is often used to store solar energy in homes to heat water. The water itself acts as the means to store solar energy. A tank is filled with hot water during the day and used when it’s required. Swimming pools can also be heated using solar energy. The water in the pool may act as a storage medium or a packed bed may be used instead. Solar energy can be used to heat homes. In this case a lot more energy is needed.
This means that larger solar panels need to be used to store solar energy. Heat-of-fusion storage units are usually used for this purpose but packed bed or hot water tanks are also sometimes used. It can be quite expensive to purchase large panels and a storage system to heat a large building. If a building is heated by solar power passive collectors are used with other storage systems.
One type of passive energy collector is the incidental heat trap. In this system heat enters through a window and falls on a stone floor. During the day the floor absorbs the heat and stays cool. At night the heat is released and heating is achieved. Another way to store solar energy is thermo-siphoning walls or roofs. In this system the heat that is absorbed and wasted in the walls and roof can be channeled for heating the home.
Solar Power: Advantages and Disadvantages
There are many advantages of solar energy. Just consider the advantages of solar energy over that of oil:
· Solar energy is a renewable resource. Although we cannot utilize the power of the sun at night or on stormy, cloudy days, etc., we can count on the sun being there the next day, ready to give us more energy and light. As long as we have the sun, we can have solar energy (and on the day that we no longer have the sun, you can believe that we will no longer have ourselves, either).
· Oil, on the other hand, is not renewable. Once it is gone, it is gone. Yes, we may find another source to tap, but that source may run out, as well.
· Solar cells are totally silent. They can extract energy from the sun without making a peep. Now imagine the noise that the giant machines used to drill for and pump oil make!
· Solar energy is non-polluting. Of all advantages of solar energy over that of oil, this is, perhaps, the most important. The burning of oil releases carbon dioxide and other greenhouse gases and carcinogens into the air.
· Solar cells require very little maintenance (they have no moving parts that will need to be fixed), and they last a long time.
· Although solar panels or solar lights, etc., may be expensive to buy at the onset, you can save money in the long run. After all, you do not have to pay for energy from the sun. On the other hand, all of us are aware of the rising cost of oil.
· Solar powered lights and other solar powered products are also very easy to install. You do not even need to worry about wires.
As you can see, there are many advantages of solar energy. The advantages of solar energy range from benefiting your pocketbook to benefiting the environment. There are actually only a few features of solar energy that can be considered disadvantages.
Here are the disadvantages of solar energy:
· Solar cells/panels, etc. can be very expensive.
· Solar power cannot be created at night.
As you can see the advantages of solar energy create a much longer list that the disadvantages, and the disadvantages are things that can be improved as technology improves.
Anne Clarke writes numerous articles for websites on gardening, parenting, the enviornment, fashion, and home decor. Her background includes teaching and gardening. For more of her articles on solar power, please visit Solar Home.
Advantages of solar energy
There are many advantages of solar energy. Just consider the advantages of solar energy over that of oil:
- Solar energy is a renewable resource. Although we cannot utilize the power of the sun at night or on stormy, cloudy days, etc., we can count on the sun being there the next day, ready to give us more energy and light. As long as we have the sun, we can have solar energy (and on the day that we no longer have the sun, you can believe that we will no longer have ourselves, either).
- Oil, on the other hand, is not renewable. Once it is gone, it is gone. Yes, we may find another source to tap, but that source may run out, as well.
- Solar cells are totally silent. They can extract energy from the sun without making a peep. Now imagine the noise that the giant machines used to drill for and pump oil make!
- Solar energy is non-polluting. Of all advantages of solar energy over that of oil, this is, perhaps, the most important. The burning of oil releases carbon dioxide and other greenhouse gases and carcinogens into the air.
- Solar cells require very little maintenance (they have no moving parts that will need to be fixed), and they last a long time.
- Although solar panels or solar lights, etc., may be expensive to buy at the onset, you can save money in the long run. After all, you do not have to pay for energy from the sun. On the other hand, all of us are aware of the rising cost of oil.
- Solar powered lights and other solar powered products are also very easy to install. You do not even need to worry about wires.
As you can see, there are many advantages of solar energy. The advantages of solar energy range from benefiting your pocketbook to benefiting the environment. There are actually only a few features of solar energy that can be considered disadvantages.
Here are the disadvantages of solar energy:
- Solar cells/panels, etc. can be very expensive.
- Solar power cannot be created at night.
As you can see the advantages of solar energy create a much longer list that the disadvantages, and the disadvantages are things that can be improved as technology improves.
Rising oil prices makes renewable energy attractive
With fuel prices soaring, renewable energy is being promoted by the state government here.
The West Bengal Green Energy Development Corporation Ltd (WBGEDC), a government agency floated for the development of green energy, is likely to come up with "renewable policy energy" framework by the end of this year
The focus areas of the policy would be to formulate certain concessions to be given to those using renewable energy, like rebate in municipal tax among other benefits, said S P Gon Chaudhuri, managing director of WBGEDCL, on the sidelines of a press conference to announce its tie-up with a Kolkata-based real estate developer to transfer green energy techniques, in Kolkata on Wednesday.
The tariff policy on the use of renewable energy was already in place in West Bengal, said Gon Chaudhuri. The policy would be divided into two parts, covering benefits to the people residing in buildings where renewable energy was being used, and independent power producers, he said. This apart, the policy will also promote the use of bio-fuels, by giving certain concessions to farmers undertaking Jatropha cultivation.
The corporation would assist the farmers in procuring Jatropha seeds and selling the end products in the market, he said. The states of Mizoram and Tripura, and union territory of Andaman and Nicobar, have also approached the WBGEDC for framing a similar policies.
"We would act as a consultant for preparing a renewable energy policy for states like like Mizoram and Tripura," he said.
The policy would be formulated with help from Indian Institute of Social Welfare and Business Management (IISWBM), he added. It will be placed before the state cabinet by the end of this year.
Benefits of Renewable Energy
Renewable energy can supply a significant proportion of the United States' energy needs, creating many public benefits for the nation and for states and regions, including environmental improvement, increased fuel diversity and national security, and regional economic development benefits.
Environmental Benefits
Using fossil fuels -- coal, oil and natural gas -- to make electricity dirties the nation's air, consumes and pollutes water, hurts plants and animal life, creates toxic wastes, and causes global warming. Using nuclear fuels poses serious safety risks. Renewable energy resources can provide many immediate environmental benefits by avoiding these impacts and risks and can help conserve fossil resources for future generations. Of course, renewable energy also has environmental impacts. For example, biomass plants produce some emissions, and fuel can be harvested at unsustainable rates. Windfarms change the landscape, and some have harmed birds. Hydro projects, if their impacts are not mitigated, can greatly affect wildlife and ecosystems. However, these impacts -- which are discussed in Appendix A -- are generally much smaller and more localized than those of fossil and nuclear fuels. Care must nevertheless be taken to mitigate them.
Air Pollution
Clean air is essential to life and good health. Air pollution aggravates asthma, the number one children's health problem. Air pollution also causes disease and even premature death among vulnerable populations, including children, the elderly, and people with lung disease. A 1996 analysis by the Natural Resources Defense Council of studies by the American Cancer Society and Harvard Medical School suggests that small particles in the air may be responsible for as many as 64,000 deaths each year from heart and lung disease.[1] As the figure below shows, air pollution is responsible for more deaths than motor vehicle accidents, and ranks higher than many other serious health threats.[2] A few of the most important pollutants are discussed below.[3]
Sulfur oxides
Electricity production, primarily from burning coal, is the source of most emissions of sulfur oxides (SOx), as the figure shows. These chemicals are the main cause of acid rain, which can make lakes and rivers too acidic for plant and animal life. Acid rain also damages crops and buildings. National reductions in sulfur oxides required by the Clean Air Act Amendments of 1990 may not be sufficient to end damage from acid rain in the northeastern United States.[4] SO2 is also a primary source of fine particles in the air.
Nitrogen oxides
Burning fossil fuels either to produce electricity or to power transportation emits nitrogen oxides (NOx) into the air. In the presence of sunlight, nitrogen oxides combine with other chemicals to form ground-level ozone (smog). Both nitrogen oxides and ozone can irritate the lungs, cause bronchitis and pneumonia, and decrease resistance to respiratory infections. In addition, research shows that ozone may be harmful even at levels allowed by federal air standards. The U.S. Environmental Protection Agency (EPA) has published a new rule reducing nitrogen oxide emissions from 0.12 parts per million to 0.08 parts per million. States have until 2003 to submit plans for meeting the new standard and up to 12 years to achieve it.[5]
Carbon dioxide
Carbon dioxide (CO2) is the most important of the greenhouse gases, which contribute to global warming by trapping heat in the earth's atmosphere. Electricity generation is, as the figure shows, the largest industrial source of carbon dioxide emissions and a close second to the transportation sector.
Samples from air bubbles trapped deep in ice from Antarctica show that carbon dioxide and global temperature have been closely linked for 160,000 years. Over the last 150 years, burning fossil fuels has resulted in the highest levels of carbon dioxide ever recorded. In 1995, the Intergovernmental Panel on Climate Change -- an authoritative international scientific body -- concluded that "the balance of evidence suggests that there is a discernible human influence on global climate."[6] All 10 of the warmest years on record have occurred in the last 15 years. The 1990s have already been warmer than the 1980s -- the warmest previous decade on record, according to the Goddard Institute of Space Studies.[7]
Without action, carbon dioxide levels would double in the next 50 to 100 years, increasing global temperatures by 1.8 to 6.3 degrees Fahrenheit. The heat trapped in the atmosphere would cause expansion of the ocean's volume as surface water warms and melt some glaciers. A two-foot rise in sea level could flood 5,000 square miles of dry land in the United States, and another 5,000 square miles of coastal wetlands, as the figure shows. From 17 to 43 percent of coastal wetland-prime fish and bird habitat-could be lost. Building dikes and barriers could reduce flooding of dry land, but would increase wetland loss. Impacts on island nations and low-lying countries, like Egypt and Bangladesh, would be much worse.
Altered weather patterns from changes in climate may result in more extreme weather events. Some areas will suffer more drought and others more flooding, putting crop production under great stress in some regions. The character of our forests could change dramatically. Other expected impacts include an increase in heat-related deaths, increased loss of animal and plant species, and the spread of pests and diseases into new regions with less resistance to them.[8]
In 1997, at a conference in Kyoto, Japan, the developed nations of the world agreed to reduce carbon dioxide emissions. The United States agreed to 7 percent reductions from 1990 levels by the period 2008-2012. Senate ratification of this agreement remains uncertain, however.
Sun Power - the real power
SunPower, which makes solar cells and panels, says it has boosted the efficiency and size of its solar panels, yielding substantially more electricity than current panels.
The San Jose, Calif.-based company on Monday announced its second-generation, higher-power product at the Solar Power 2006 conference, and the panels are expected to be in mass production next year.
SunPower says it has managed to increase efficiency of the silicon cells from 20 percent to 22 percent. Further, the 5-foot by 3-and-a-half-foot panels will pack 96 individual cells within them, compared to the 72 contained in the company?s current product.
Overall, these changes result in a 43 percent increase in power, said Julie Blunden, vice president of external affairs at SunPower. Each panel can generate 315 watts of electricity and will have roughly the same cost per watt as the existing line, she said.
The theoretical limit of monocrystalline silicon cell efficiency is about 25 percent, Blunden said.
Other companies are developing solar photovoltaic manufacturing techniques around other materials, notably CIGS (copper indium gallium selenide).
But SunPower, which is owned by Cypress Semiconductor, intends to continue investing in higher solar efficiency and ways to lower the cost of installation, Blunden said.
Sunlight Solar Energy
Sunlight Solar Energy, Inc. is one of the leading photovoltaic design and installation corporations in the US and is an approved contractor under energy fund photovoltaic programs in 5 states.
SSE quotes you a complete "turnkey" solar photovoltaic installation, including all necessary paperwork, permits and contracts. Sunlight Solar Energy, Inc. is a premier dealer of SunPower.
SunPower panels and inverters are high performance and intelligent design.
Read more...
Solar Energy – Turning Sunlight into Electricity
Solar energy could be used to generate electricity on a large scale if solutions were found for certain problems. At present it is too difficult to produce large amounts of solar energy and store it for times when the sun is not available such as overnight, on overcast days or at high latitudes. However let’s take a look at the way in which sunlight can be turned in a source of electrical power.
Solar energy keeps us all alive. The heat and light from the sun is what keeps the earth at the correct temperature. It is the sun’s energy that keeps almost all living organisms alive. It is the sun that determines natural systems and cycles. About 95% of the energy from the sun is given off as light that we can see. However the light that we can see is only a small amount of the sun’s total energy.
The "photovoltaic effect" is a process through which a PV cell changes sunlight into electricity. The light from the sun is made up of photons. These are particles of solar energy. Depending on their wavelengths, each photon contains different amounts of energy. When photons strike a PV cell they are reflected, absorbed, or pass right through.
So how does solar energy produce electricity? When a photon is absorbed it can generate electricity. Then the energy of the photon is transferred to an electron in the PV cell (a semiconductor). The electron escapes and becomes part of an electrical circuit. When it escapes it makes a tiny hole. The PV cell has a built-in electric field. This enables the cell to provide the voltage needed to drive the electrical current into a light bulb.
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Generating Power from Solar Energy
How Sunlight is Converted to Electricity Using Photovoltaic Process
Solar power is electricity that is generated from sunlight, and is a common choice of renewable energy for households and for large companies. There are two basic forms of solar power in current use: photovoltaics and solar thermal power.Photovoltaic Solar Power
Photovoltaic systems, such as conventional solar panels, directly convert sunlight into energy using the principles of the photovoltaic effect. The photovoltaic effect takes advantage of the properties of semiconductor materials, with silicon being the primary material used in photovoltaic solar cells. When photons strike the solar cell, electrons in the semiconductor material are shaken loose, allowing them to flow as electricity. This electricity is direct current (DC), and can be directly used to charge batteries, or can be connected to an inverter to power alternating current (AC) components, or to be connected to the local electrical grid.
Traditional photovoltaic systems are based on silicon. Silicon ingots are sliced into wafers that are fabricated into cells. Cells are combined into modules, which are packaged into end-user systems. Silicon-based solar cells have efficiencies of approximately 14-19%. However, newer systems that use gallium arsenide, another semiconductor material, can be made into thinner and more flexible modules. These "thin film" modules can presently produce efficiencies up to 30%, but currently cost more to fabricate than traditional silicon-based modules.
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