Scientists make solar energy breakthrough

Researchers at Canada's National Institute for Nanotechnology (NINT) and the University of Alberta say they have engineered an approach that is leading to improved performance of plastic solar cells (hybrid organic solar cells). The development of inexpensive, mass-produced plastic solar panels is a goal of intense interest for many of the world's scientists and engineers because of the high cost and shortage of the ultra-high purity silicon and other materials normally required.


Plastic solar cells are made up of layers of different materials, each with a specific function, called a sandwich structure. Jillian Buriak, a professor of chemistry at the U of A, NINT principal investigator and member of the research team, uses a simple analogy to describe the approach:

"Consider a clubhouse sandwich, with many different layers. One layer absorbs the light, another helps to generate the electricity, and others help to draw the electricity out of the device. Normally, the layers don't stick well, and so the electricity ends up stuck and never gets out, leading to inefficient devices. We are working on the mayonnaise, the mustard, the butter and other 'special sauces' that bring the sandwich together, and make each of the layers work together. That makes a better sandwich, and makes a better solar cell, in our case".

After two years of research, these U of A and NINT scientists have, by only working on one part of the sandwich, seen improvements of about 30 per cent in the efficiency of the working model.

Michael Brett, professor of electrical and computer engineering, NINT principal investigator and member of the research team is optimistic saying: "our team is so incredibly cross-disciplinary, with people from engineering, physics and chemistry backgrounds all working towards this common goal of cheap manufacturable solar cells. This collaboration is extremely productive because of the great team with such diverse backgrounds, [although] there is still so much more for us to do, which is exciting."

The team estimates it will be five to seven years before plastic solar panels will be mass produced but Buriak adds that when it happens solar energy will be available to everyone. She says the next generation of solar technology belongs to plastic.

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The Solar Energy Breakthrough Will Change the Energy Business Landscape

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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India close to solar energy breakthrough

SOLAR cells used to tap energy from the sun are made up of photovoltaic substances such as silicon which, when combined with suitable additives and exposed to sunlight, produce electricity. Extracting crystalline silicon from the compounds in which it is found is highly energy-intensive and the element itself accounts for upto 50 per cent of the total cost of producing photovoltaic systems. Crystalline silicon for photovoltaic applications costs about Rs 1500 (US $50) per kg in the global market. A little over 25 gms of monocrystalline wafers is required to produce one watt of electricity.

Amorphous silicon has a lower silicon content and costs half as much as crystalline silicon to produce because of its non-crystalline form. The Japanese have extensively used amorphous silicon cells in solar-powered calculators and watches.

The Department of Non-conventional Energy Sources (DNES) has been exploring the use of amorphous silicon technology to reduce the cost of photovoltaic solar cells. Bharat Heavy Electricals Limited (BHEL), Bangalore division, was assigned the task of establishing a plant to produce amorphous silicon solar cells and set up one at Gurgaon, Haryana, which was commissioned in July 1992. The Rs 16-crore plant produces amorphous silicon solar cells equivalent to 500 kwp (kilowatt peak output of electricity) per shift and has an annual capacity to produce 300 kg of Silane gas, an essential raw material. During pre-commissioning runs, the plant produced over 2000 modules of solar cells with different process parameters. Efficiencies of converting solar energy into electricity exceeding 7 per cent were achieved on individual cells in the modules.

According to R K D Shah, Executive Director (corporate planning and development), BHEL, "At present the production of amorphous silicon photovoltaic cells is still in an experimental stage. Though the potential applications are many, amorphous silicon cells are still being tested and tried in various systems and applications."

Scientists at BHEL say that amorphous silicon cells have half the efficiency of crystalline silicon cells but they cost less than half as much. According to Praveen Saxena, principal scientific officer, DNES, the cost of monocrystalline silicon, used in large-scale applications, is about Rs 225 per watt, while that of amorphous silicon, as yet used only in small systems, is Rs 150 per watt. According to BHEL sources, amorphous silicon cells produced in very large quantities can bring down the cost of solar panels to Rs 60 per peak watt.

Research in India has focused on increasing the efficiency of amorphous silicon, which is also unstable and loses efficiency at high temperatures.

Efficiency levels of over 12 per cent have been achieved by the Bangalore unit of BHEL. It has produced solar cells of 10 cm diameter which have achieved upto 14.3 per cent efficiency -- the highest achieved in the country so far. The conversion efficiency of photovoltaic devices in the international market is around 17.5 per cent.

Work on photovoltaic solar cells began in India as early as October 1980, when the Central Electronics Limited, Sahibabad, was established to produce monocrystalline silicon cells.

A separate technology mission was, therefore, set up for the development of amorphous silicon technology in the seventh plan. Prime Minister P V Narasimha Rao, who has taken particular interest in solar energy development, asserted in Parliament, "We are at the point of achieving a breakthrough in commercial applications of photovoltaic technology."

S Mehrotra, an official at BHEL, says, "When we started working on the amorphous silicon technology, we were perhaps 15 to 20 years behind the developed countries. But now we have definitely closed the gap."

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