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There are reasons to be wary of the frantic promotion of solar photovoltaic electricity, lithium-ion battery storage and electric cars, and the neglect of solar thermal power

A solar thermal power plant in Rajasthan, India (Photo by Brahma Kumaris)

Over two years ago, Prime Minister Narendra Modi drew praise from the world by taking the lead, with France, in forming an International Solar Alliance of tropical countries to harness the energy of the sun. On Sunday, March 4, that initiative took concrete shape in New Delhi.

The Indian media treated this as a diplomatic coup for Modi, and the international media took it as a sign that India, the second most populous country in the world with fossil fuel consumption rising at 7.5% a year, was taking seriously its responsibility to control greenhouse gas emissions.

But these expectations will only be fulfilled if New Delhi and Paris are able to steer the alliance away from the blind alley into which so-called green corporations and powerful governments have been dragging the world for the past five years. This is the frantic promotion of solar photovoltaic (SPV) electricity, lithium-ion battery storage and electric cars, and the increased neglect, now compounded by active denigration, of concentrated solar-thermal (CSP) power, and biomass-based transport fuels.

Obsessed with photovoltaic

In the field of power generation, this has been so effective that virtually every advertisement of solar energy anywhere in the world shows only solar PV panels. This is despite the fact that photovoltaic power simply cannot meet more than a small fraction of the world’s need for electricity. There are two reasons for this, one well known and the other only just coming to light.

The first is that the sun’s light can only be tapped when it is shining and is some distance above the horizon. This limits direct energy production from it, even in the best of circumstances, to about eight hours a day. Allowing for the 30 to 90 days when clouds, haze or dust storms obscure the sun, this allows SPV plants to supply power for no more than a quarter of the 8,760 hours in a year.

The only way to extend this is through batteries. But battery storage is horrifyingly expensive today. Proponents of SPV power point out that this cost is falling dramatically, but a study published by the World Energy Council has shown that this will only drop from the 2015 level of 12-80 US cents a unit to 6-23 US cents by 2030.

If solar PV has to be synchronised with wind and other forms of renewable energy, the cost of the so-called smart grids that will be needed will take even more of the shine out of solar PV power, and in all probability make it uneconomic.

Scarcity of rare metals

PV power’s insurmountable barrier is not, however, the cost of storage but the absolute scarcity of the rare metals needed to make the solar panels and batteries. These are cadmium, tellurium and lithium. The current generation of PV panels uses a thin film of cadmium telluride to achieve its near 20% conversion efficiency. One megawatt of SPV generating capacity requires 91 kg of tellurium and 83 kg of cadmium.

Tellurium is a by-product of copper mining. About 800 tonnes can be extracted from the copper ore that is being mined today, but only 120 tonnes are actually being produced. The precise amount of tellurium in the earth’s crust is not known, but it is estimated to be around the same as platinum, which is three times rarer than gold. That would make it around 70,000 tonnes.

Cadmium is extracted from zinc ores, of which it forms a three in ten thousandth part. Its total minable reserve is therefore estimated to be around 570,000 tonnes.

The world consumed 22,000 terawatt hours (million MWh) of power from 6.1 million MW of generating capacity in 2017. To supply the two-thirds that is now generated from coal, oil and gas with solar PV power will require installing around 7 million MW of solar panels. These panels will require 650,000 tonnes of tellurium, and 580,000 tonnes of cadmium. That is all the presently accessible cadmium and up to 10 times the accessible tellurium in the Earth’s crust.

Lithium is relatively more abundant. Till last year the US Geological Survey placed the minable content in the earth’s crust at around 14 million tonnes, but has now raised it to 40 million tonnes. The demand for lithium for storage batteries alone, to meet the nighttime demand for electricity, will come to a minimum of 4.8 million tonnes. But that is without taking electric cars into account.

The total number of cars on the road crossed 1 billion in 2010, and is expected to reach 2.5 billion by 2050. Battery-powered cars like the Tesla require an average of 12.7 kg of lithium. With country after country blindly announcing that they will replace liquid fuel-driven cars with electric cars, it is worth remembering that, even with a 25% increase in battery efficiency, an all-electric global fleet in 2050 will require over 30 million tonnes of lithium.

These calculations show that, as has happened with ethanol, not long after the world starts shifting to these technologies, the rising demand for these metals will push their prices into the stratosphere, and bring the shift to a halt. By then another decade will have been lost — time that the world can no longer afford.

Solar thermal power

Salvation lies not in solar PV but solar thermal power. Concentrated Solar Power (CSP) plants require only mild steels, aluminium, and silver-backed mirrors to generate power. Solar thermal power has the inestimable advantage that by using molten salt instead of water to capture the sun’s heat, it can provide steam to the turbines at temperatures as high as 1,000 degrees Celsius, which is far higher than the 593 degrees currently needed by the most advanced supercritical boilers in the conventional power industry.

What is far more important, when stored in well-designed tanks, a mixture of molten sodium and potassium nitrates has been found to lose as little as 1% of its heat in 24 hours. As a result, solar thermal power plants in Spain, Morocco, Dubai, Saudi Arabia, South Africa and elsewhere are now supplying 18 to 20 hours of guaranteed power from solar heat alone.

Best of all, CSP prices are also plummeting, from 15.9 US cents (INR 11.60) a unit in the third phase of the 540 MW plant completed at Ouarzazate in Morocco only a year ago to 7.3 US cents (INR 4.90) for a giant 700 MW plant to be constructed in Dubai by 2020.

While Modi has been making grand promises about what India will do in solar energy, India has fallen steadily behind even small developing countries in performance. In 2013, there were nine 50 to 100 MW CSP plants on the drawing boards. Today, only two are operational, and there is not a single solar thermal power plant, large or small, on the drawing board.

High costs

The cause is that while CSP plants can deliver up to four times as much power as SPV plants, they also cost nearly four times as much to build. This makes the cost of the plant highly sensitive to interest rates and delays in the provision of infrastructure by the state. India’s prohibitive interest rates (11% against Dubai’s 4%) and the huge delays that the bureaucracy has imposed on the pioneers in this field, have made sure that no one will venture into CSP power plants, in spite of the fact that India has more than 50,000 sq. km of hot and cold desert available for setting them up.

Prior to launching its 700 MW project, the Dubai Electricity and Water Authority divided its detailed planning into four parts: legal framework, infrastructure, finance and skill building. Construction began only after all four were in place. India could learn from Dubai’s example.


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