Wind and Solar Power

Dish Stirling Systems of SBP in Spain

Solar Power

It cannot possibly have escaped anyone's attention that earth has a limited supply of fossil fuels. We use fossil fuels for the bulk of our energy requirements, and those requirements continue to grow. As the finite supply of these fuels comes the point where they are in short supply, the inevitable consequence is war for these resources. But there are alternatives.

Solar power, or energy is the light and radiant heat from the Sun that influences Earth's climate and weather and sustains life. Solar power specifically refers to electricity generated from solar radiation, which, along with secondary solar resources such as wind and wave power, hydroelectricity and biomass account for most of the available renewable energy on Earth. Most arguments against using wind and solar power would seem to be political or financial obstacles rather than genuine reasons. All the time the governments are owned by big business, this will not change. The simple fact is that it is possible to power a "normal" house using wind and solar power without being beholden to an energy supply company in most parts of the world.

This blog is a discussion on the practical possibility and options available if you choose to use renewable energy instead of relying on the political machine to supply your every need.

Solar energy technologies can provide electrical generation by heat engine or photovoltaic means; space heating and cooling in active and passive solar buildings; potable water via distillation and disinfection, daylighting, hot water, thermal energy for cooking, and high temperature process heat for industrial purposes.

Sunlight, in the broad sense, is the total spectrum of the electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the atmosphere, and the solar radiation is obvious as daylight when the Sun is above the horizon. This is usually during the hours known as day. Near the poles in summer, sunlight also occurs during the hours known as night and in the winter at the poles sunlight may not occur at any time. When the direct radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and heat. Radiant heat directly produced by the radiation of the sun is different from the increase in atmospheric temperature due to the radiative heating of the atmosphere by the sun's radiation. Sunlight may be recorded using a sunshine recorder, pyranometer or pyrheliometer. The World Meteorological Organization defines sunshine as direct irradiance from the Sun measured on the ground of at least 120 W·m⁻².

Direct sunlight has a luminous efficacy of about 93 lumens per watt of radiant flux, which includes infrared, visible, and ultra-violet light. Bright sunlight provides luminance of approximately 100,000 candela per square meter at the Earth's surface.

The Earth receives 174 petawatts (PW) of incoming solar radiation (insolation) at the upper atmosphere. Approximately 30% is reflected back to space while the rest is absorbed by clouds, oceans and land masses. The spectrum of solar light at the Earth's surface is mostly spread across the visible and near-infrared ranges with a small part in the near-ultraviolet.

The absorbed solar light heats the land surface, oceans and atmosphere. The warm air containing evaporated water from the oceans rises, driving atmospheric circulation or convection. When this air reaches a high altitude, where the temperature is low, water vapor condenses into clouds, which rain onto the earth's surface, completing the water cycle. The latent heat of water condensation amplifies convection, producing atmospheric phenomena such as cyclones and anti-cyclones. Wind is a manifestation of the atmospheric circulation driven by solar energy. Sunlight absorbed by the oceans and land masses keeps the surface at an average temperature of 14 °C. The conversion of solar energy into chemical energy via photosynthesis produces food, wood and the biomass from which fossil fuels are derived.

Solar radiation along with secondary solar resources such as wind and wave power, hydroelectricity and biomass account for 99.97% of the available renewable energy on Earth.

The Sun's Energy

The total solar energy absorbed by Earth's atmosphere, oceans and land masses is approximately 3,850 zettajoules (ZJ) per year. In 2002, this was more energy in one hour than the world used in one year. Photosynthesis captures approximately 3 ZJ per year in biomass. The amount of solar energy reaching the surface of the planet is so vast that in one year it is about twice as much as will ever be obtained from all of the Earth's non-renewable resources of coal, oil, natural gas, and mined uranium combined.

From the table of resources it would appear that solar, wind or biomass would be sufficient to supply all of our energy needs, however, the increased use of biomass has had a negative effect on global warming and dramatically increased food prices by diverting forests and crops into biofuel production. As intermittent resources, solar and wind raise other issues.

Wind Power

Wind Power - Image credit

Wind power is the conversion of wind energy into a useful form, such as electricity, using wind turbines. At the end of 2007, worldwide nameplate capacity of wind-powered generators was 94.1 gigawatts. Although wind produces only about 1% of world-wide electricity use, it is growing rapidly, increasing more than fivefold globally between 2000 and 2007. In several countries it has achieved relatively high levels of penetration, accounting for approximately 19% of electricity production in Denmark, 9% in Spain and Portugal, and 6% in Germany and the Republic of Ireland in 2007.

Wind energy has historically been used directly to propel sailing ships or converted into mechanical energy for pumping water or grinding grain, but the principal application of wind power today is the generation of electricity. Large scale wind farms are typically connected to the local electric power transmission network, with smaller turbines being used to provide electricity to isolated locations. Utility companies increasingly buy back surplus electricity produced by small domestic turbines. Wind energy as a power source is favored by many environmentalists as an alternative to fossil fuels, as it is plentiful, renewable, widely distributed, clean, and produces lower greenhouse gas emissions, although the construction of wind farms is not universally welcomed due to their visual impact and other effects on the environment. The intermittency of wind seldom creates problems when using wind power to supply a low proportion of total demand. Where wind is to be used for a moderate fraction of demand, additional costs for compensation of intermittency are considered to be modest.

Humans have been using wind power for at least 5,500 years to propel sailboats and sailing ships, and architects have used wind-driven natural ventilation in buildings since similarly ancient times. The use of wind to provide mechanical power came somewhat later in antiquity.

The Babylonian emperor Hammurabi planned to use wind power for his ambitious irrigation project in the 17th century BC. An early historical reference to a rudimentary windmill was used to power an organ in the 1st century AD. The first practical windmills were later built in Sistan, Afghanistan, from the 7th century. These were vertical-axle windmills, which had long vertical drive shafts with rectangle shaped blades. Made of six to twelve sails covered in reed matting or cloth material, these windmills were used to grind corn and draw up water, and were used in the grist milling and sugarcane industries. Horizontal-axle windmills were later used extensively in Northwestern Europe to grind flour beginning in the 1180s, and many Dutch windmills still exist.

In the United States, the development of the "water-pumping windmill" was the major factor in allowing the farming and ranching of vast areas of North America, which were otherwise devoid of readily accessible water. They contributed to the expansion of rail transport systems throughout the world, by pumping water from wells to supply the needs of the steam locomotives of those early times. The multi-bladed wind turbine atop a lattice tower made of wood or steel was, for many years, a fixture of the landscape throughout rural America.

The American Charles F. Brush is often credited with being the first person to produce electricity using a wind powerd machine, however, Brush first used his wind turbine during the winter of 1887, and in July of that year, a Scottish academic, Professor James Blyth, had been undertaking similar experiments which culminated in a UK patent in 1891. Blyth's 33 foot high, cloth-sailed wind turbine was installed in the garden of his holiday cottage at Marykirk in Scotland and was used to charge accumulators developed by the Frenchman Camille Alphonse Faure, to power the lighting in the cottage, thus making it the first house in the world to have its electricity supplied by wind power. Blyth offered the surplus electricity to the people of Marykirk for lighting the main street, however, they turned down the offer as they thought electricity was "the work of the devil." Although he later built a wind machine to supply emergency power to the local Lunatic Asylum, Infirmary and Dispensary of Montrose the invention never really caught on as the technology was not considered to be economically viable.

In the 1890's a Dane, Poul la Cour, constructed wind turbines to generate electricity, which was then used to produce hydrogen. 

The first modern wind turbines were built in the early 1980s, although more efficient designs are still being developed.