Mean Green

We live on a solar powered planet.  Virtually all of the energy we use comes — ultimately — from the sun.

Fossil fuels, including petroleum, coal, and natural gas, originated from ancient biomass which relied on photosynthesis powered by the sun.

Most of our renewable energy likewise starts with the sun.  Wind power is driven primarily by convection currents created by the sun’s rays heating the sea and land.  Biofuels, including bioethanol and biodiesel, begin with plants using the sun to power photosynthesis.  Hydroelectric power — whether dams or in-stream turbines — relies on the downstream flow of water that fell as rain or snow but which originally evaporated from lakes and oceans due to heat from the sun.

More obvious are the applications of solar thermal and solar photovoltaic power.

Solar Thermal

The sun is a giant nuclear fusion reactor with a surface temperature of more than 5,000 degrees Celsius (9,000 degrees Fahrenheit).  Of course, only a minute fraction of its energy reaches the Earth, and only part of that energy is heat.  But we can take advantage of that heat simply by opening our curtains on a winter day to let the sun warm our home.  Or we may put a coil of black tubing on the roof of our house with water running through it to provide hot water.

Using the sun’s heat to produce electricity is only a little more complicated.  Focus the sun’s rays on a container of water to turn the water into steam under pressure.  Use the steam to drive a turbine, which then drives a generator producing electricity.

On a large scale, solar thermal systems often consist of hundreds or even thousands of flat mirrors focusing the sun’s rays on central towers, or long troughs of concave mirrors focused on tubes.  Such arrays can produce power in the range of 100 megawatts or more, much less than coal fire and nuclear plants, but with none of the environmental risks.

Solar Photovoltaic

A more direct method of producing electricity from the sun is solar photovoltaic.  This technology relies on the properties of certain materials to act as photodiodes.  When photons of light strike the material, they energize electrons, producing a direct current.  Although each interaction produces very little energy, the flow can be combined so that cells and arrays of cells can deliver substantial power.  Like solar thermal systems, large solar photovoltaic arrays may cover thousands of square meters and cost millions of dollars.

Putting Solar To Use

Advances in photovoltaic technology have brought solar-based electricity to the general public.  Homeowners and businesses can have their own rooftop arrays, producing their own power independent of the public utility grid.  Rooftop solar panel kits that include an inverter to convert the panel’s direct current into household alternating current are available from building supply companies and online retailers for a few hundred dollars.

To help them reach commitments made in international agreements to reduce greenhouse gas emissions, many governments encourage public involvement in renewable energy projects by providing tax incentives, grants, rebates, and interest-free loans to individuals setting up their own solar and wind projects.

Smart meters may allow homeowners or businesses to produce a portion of the power they use, and even to sell excess power back to the utility grid.

Setting up your own solar power system isn’t difficult, but you should be aware of local laws governing the size and type of installation allowed.  There may also be insurance concerns if you plan on mounting panels on your roof.  Also, tracking down and obtaining government incentives can be a complex process.  Thus, it may be wise to seek the advice of a qualified consultant specializing in small-scale renewable energy systems.

The sun is an incomparable gift that shines for everyone.  All we need to do is to put it to use.