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Debate: For and against solar energy - can it be clean, cheap and ubiquitous?

One of the Grand Challenges for Engineering is to ‘make solar energy economical’. Can it be clean, cheap and ubiquitous? We ask two experts with radically different views.

For: Solar energy already makes economic sense and its applications can be increased immediately

By Gage Williams

Generating your own electricity is akin to ‘home brewing’ beer. I live in Cornwall where my grid supply comes either from Hinkley Point (85 miles) or from Didcot, which is 205 miles away. A kWh generated at Didcot costs about 5p. But by the time it has passed through the National Grid, to Western Power Distribution, to one of the ‘Big Six’ supply companies and to my house, the daytime cost has risen to about 20p. To pay this, as a 20 per cent taxpayer, I would need to earn 25p. Instead, I have installed 4kW of solar PV ground-mounted in my garden (it will make an excellent garden shed) that today would cost £5,000. Adding £1,000 for the replacement of the inverter at some stage should give me 4,000kWh per year for 30 years (I recently saw solar PV panels that were 34 years old and generating 90 per cent of their original output). Amortising the cost by dividing it by the lifetime output gives the home brew cost of my electricity as 5p/kWh, a saving of 20p/kWh. And this is without any subsidy.

Some would argue that large solar farms use up farmland that should be used for growing food.  Instead, we are finding that solar and sheep mix well together, with the sheep using the panels for shelter while keeping the grass trimmed. The grass grows better due to less wind and less dew to burn off while the spacing of the rows of panels ensures that there is sufficient sunshine for growth.

Those with space can generate solar electricity. Farm tractors should switch to electricity using interchangeable battery packs. Farms have the machinery to change a battery pack. Tractors using lightweight electric motors will need the weight provided by the batteries. Unlike electric cars, they have neither the range nor the space problem requiring expensive high-energy density batteries. If forklift trucks can go electric (to reduce emissions in buildings), there is no reason why tractors should not, too.

Solar PV works well with other renewable technologies such as ground, water and air source heat pumps, where each kWh of cheap solar electricity can be converted into 4kWh of heat or cooling. Intermittency can be smoothed by using surplus wind and solar electricity to pump water from a lower to a higher reservoir and run it back as hydro-electricity when the grid or local user most needs it.

Cornwall, for example, has 12,000 acres of China claylands, one of the largest brownfield sites in Europe, which is covered in disused claypits such as the Eden Project. The area, with elevations over 1,000ft, has high wind-speeds and excellent insolation. A combination of wind-turbines and solar PV could generate more electricity than Cornwall currently uses with the surplus available for pumped storage using the claypits. This could become a massive power battery for the south of England and enable the grid to be balanced more effectively as hydro-electricity is almost instantaneous.

With electric vehicles, there is logic to providing car parks with solar PV canopies as well as making better use of large roofs on buildings such as supermarkets and warehouses so that vehicles can be recharged while using the car park.

Finally, we need also to look at using DC generated by solar PV. This would not only cut the cost as inverters would no longer be needed, but would provide houses and SMEs with a direct source for the many gadgets and laptops, for instance, that run on 12V or 24V DC. Surplus electricity could be stored during daytime using cheap lead acid batteries that have been well proven by the car industry.

Now that LED lighting can run on DC, there is no reason why all domestic lighting should not switch and save a further 50 per cent on the cost of low-energy bulbs or 90 per cent on filament ones.

Home brew DC could become the norm with the grid providing back up and power for heavier appliances.

Against: Solar energy may appear to have the potential to be economical but there are hidden costs

By Ozzie Zehner

Down the street from my house in San Francisco, Royal Dutch Shell is preparing to build a massive solar array in one of the foggiest urban microclimates on Earth. In this deal, which the Wall Street Journal identifies as a ‘victory’ for the oil company, tens of millions of taxpayer dollars will flow away from public programs to subsidise superfluous energy production. As engineers, we have an ethical obligation to critically engage energy firms and researchers in promoting their various energy schemes. Solar cells may be marketed as green, but they are harmful to the environment and human prosperity for several reasons.

First, solar cells are hardly clean. They contain heavy metals that can leach into groundwater when disposed at the end of their lifecycle. Photovoltaic manufacturers also employ toxic and explosive compounds that can lead to unintended health risks for workers and local residents. Scientists are discovering the same types of short- and long-term harms that concerned citizens have historically rallied against.

Second, it takes power to make power. Humans use dirty fossil fuels because their energy is dense, portable, storable, fungible and transformable into other products. When we expend those finite resources to build solar arrays, we are left with energy that is not dense, but diffuse. Solar energy is not readily portable, storable, fungible or transformable. These limitations and their associated environmental impacts aren’t easily measured and so they typically do not show up in official solar analyses.

Third, there’s no evidence to support the assumption that solar cells are a zero carbon energy technology. A study in Nature Climate Change by University of Oregon researcher Richard York, points to just the opposite. Solar cells don’t offset fossil fuel or carbon footprints in practice – they are merely a green illusion. Solar cells rely on fossil fuels for mining, fabrication, installation and maintenance. They also require conventional power plants, or storage mechanisms such as batteries, with additional layers of environmental impacts.

We’ve been promised that solar cells will become efficient and affordable. Today the only difference is that these fairy tales are funded through the glossy PR campaigns of BP and Shell, and other energy firms.

Nevertheless, the apparent thrift of solar cells is also a slight of hand. China and other countries heavily subsidise solar cell production, which makes them seem more affordable than they actually are. The solar industry generally highlights the cost of polysilicon and the technical components of solar cells. But these represent less than half the cost of an installed solar system. The larger costs arise from installation, maintenance, insurance, as well as expenses that accrue through operating and maintaining concurrent power plants or battery backup. Newer thin film technologies degrade quicker than older models, offsetting much of the presumed benefit.

Even if solar cells were massively more efficient and less expensive, they would only serve to expand energy supplies and accelerate overall demand. Solar cells shine brightly within the idealism of textbooks, but experience reveals a scattered collection of side effects and limitations.

The real clean energy is less energy. If we wish to leave a smaller footprint on the Earth and back away from resource scarcity we should develop strategies to use far less energy overall, not subsidize more energy production.

Any number of conservation strategies offer far higher dividends than solar cell investments. We could question growth in energy production, economy, and population. All of these initiatives are left under-represented as we unwittingly rush to celebrate energy firms who are building the next round of ecological disaster machines.

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