Storing wind power in cold stores

According to Nature, a European-funded project has be launched to store gigawatts of electricity created from wind into the refrigerated warehouses normally used to store food. As the production of wind energy is variable every day, it cannot be easily accommodated on the electricity grid. So the "Night Wind" project wants to store wind energy produced at night in refrigerated warehouses and to release this energy during daytime peak hours. The first tests will be done in the Netherlands this year. And as the cold stores exist already, practically no extra cost should be needed to store as much as 50,000 megawatt-hours of energy.

Here is how Nature describes the — simple, but brilliant — idea behind this project.

The idea seems simple. Say you lowered the temperature of all large coldstores in Europe by just 1°C during the night when electricity demand is low, then let it rise 1°C by switching them off during the day when demand is at peak. The net effect would be that the warehouses would act as batteries — potentially storing 50,000 megawatt-hours of energy — and the food wouldn't melt.

Before going further, below is a diagram illustrating the idea: wind energy is optimally stored or released by following the electricity consumption patterns (Credit: Night Wind project)

In European jargon, the official denomination of the Night Wind project is "Grid Architecture for Wind Power Production with Energy Storage through load shifting in Refrigerated Warehouses." And it is led by Sietze van der Sluis, head of refrigeration and heating technology at The Netherlands Organization for Applied Scientific Research (TNO) in Delft.

Click Here to see the goals of this Night Wind Project

New 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.

Benefits of Purchasing Renewable Energy

According to the EIA, renewable energy, including hydropower and other renewables accounted for 8.8% of total U.S. energy generation in 2004. In recent years, however, there has been considerable growth in the use of renewable energy. Many state and local governments, for instance, have turned to renewable energy as a way to reduce local air pollution, reduce generation of greenhouse gases and/or stimulate the local economy. See below for more information.
Meet Greenhouse Gas Reduction Goals
In lieu of the ratification of the Kyoto Protocol by the United States, many public agencies and private businesses have voluntarily set greenhouse gas reduction goals. San Diego, for example, set a 15% GHG reduction goal in 2002 in partnership with the International Council for Local Environmental Initiatives (ICLEI). As of February 2006, 208 mayors have signed onto The US Mayors Climate Protection Agreement. These signatories have agreed to meet or exceed the Kyoto Protocol’s 7% GHG reduction goals (in comparison to 1990 levels) by 2012. For more information, go to the Pew Center on Global Change’s State and Local News page. Currently, 27 states have Climate Action Plans to reduce greenhouse gases1.

Industries and private businesses have taken initiative and partnered with the EPA Climate Leaders program to set emissions reduction goals and to monitor progress by reporting to the EPA.
Meet Air Quality Goals
Since 1990, the Federal Government, through the EPA, has set national ambient air quality standards (NAAQS) designed to regulate exposure to a list of harmful criteria pollutants. Many jurisdictions are classified as in “non attainment” and have not met these goals. Shifting to renewable energy may significantly reduce sulfur and nitrogen oxides, particularly in areas surrounding or downwind of energy production facilities. For a list of non attainment areas, visit http://www.epa.gov/air/oaqps/greenbk/

In 2004 Montgomery County included its wind purchase as an air pollution reduction strategy in the region's air quality plan, making it the first time the U.S. Environmental Protection Agency recognized wind power as a way of meeting federal air quality requirements2. For more information on this and other examples, see the EPA’s Green Power Partnership site.
Create Exportable Technology and Jobs
In the 1980’s, the US was a technological leader in solar and wind energy technology, but in the intervening years, other countries have taken the lead on many renewable technologies. A national commitment to renewable energy could allow the US to rapidly regain a position at the forefront3. Many believe that the development of domestic renewable resources could reinvigorate the local economy while helping the U.S. become more energy independent.

For example, a report published by faculty in the Energy and Resources Group and the Goldman School of Public Policy at the University of California Berkeley (Kammen et al. 2004 - http://ist-socrates.berkeley.edu/~rael/renewables.jobs.pdf ) that summarized 13 independent reports on job creation and renewable energy concluded that renewable energy generates more jobs than fossil-fuel energy for each unit of energy produced. Renewable energy operations have the potential to generate three to eleven times the number of jobs created by fossil-fuel operations, with solar and biomass exhibiting the highest potentials.

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.