If there is one main problem with solar power for homes, it would be, “How do you store the extra solar power for use at night and during grey days?”
The trouble is that it’s not easy to store electricity. Using batteries on a large scale doesn’t work so well. Energy is lost in the inverting from DC to AC. After that, the battery efficiency levels are not ideal. However, there is a new approach being applied that looks to eradicate the problem.
The ‘big idea’ is simply to capture the sun’s heat and store it, like water is stored behind a dam. The example of the simple coffee thermos shows that we are already doing this successfully in other areas. In relation to the energy from the sun, this technique is known as ‘solar thermal’.
In currently existing solar thermal power plants, the heat from the sun is focused on a mass of water which then boils up producing steam. The steam spins a turbine, creating power. The latest innovation lies in the idea of storing the heated water for long periods of time before releasing it into the above-mentioned process to generate the power.
Being able to store the solar energy in this way allows companies like Ausra, of Palo Alto, California, to supply solar power for homes after sunset or during periods of poor weather. Ausra uses Fresnel lenses to focus the light intensely, heating miles of optimized liquid in black-painted pipes.
Another company, SolarReserve, takes solar energy, stores it, puts it into a reservoir, and then uses it on demand. They use a “power tower” much like a water tank on stilts. This is 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 follows through the course of the year. Inside the tower, they use molten salt which can be heated to extremely high temperatures.
They claim that such a power tower could supply 540 megawatts of heat, effectively producing 250 megawatts of electricity. Now, that’s a lot of solar power for homes! In fact, it would be enough to power up a medium-sized city!
Using larger fields of mirrors, a tower design could be the answer for solar energy suppliers situated at higher latitudes or in less sunny places. The small start-up, eSolar that is famously backed by Google, is choosing to go down this road. Their stated aim is to make solar power for homes for less than the price of coal-fired power.
Let’s hope that Google has the same extraordinary success with their energy solutions that they have had with their search engine technology!
from Sam Deane,
your solar power for homes guide,
at www dot go solar power for homes dot com
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