> Solar Energy - how you can use the Sun

What is Solar Energy?

Simply put this is just the 'heat' sent to us by the Sun during the day. This heat is used to add energy to a device or surface to produce a desired result. This form of 'heating' can occur in two forms, either direct or indirect. The difference being that indirect heating uses some other material or substance to transfer the energy or heat to its final place of use. Direct heating essentially heats directly what you need to be heated.

Below we shall go through the main classes of Solar energy usage.

Solar Panels

This is probably what most people are familar with when they think about Solar Energy. Everybody has seen solar panels on roofs and in arrays converting the Sun's energy into electricity directly. What most people do not realize is how, currently, this is a very inefficient process.. The best so far is just under 19% efficient; i.e. 81% of the Sun's energy is 'lost' or not used.

For a more detailed discussion on Solar Panels see this article.

Solar Steam Generators

To get around this problem if efficiency with solar panels for large scale installations needing to generate electricity a different approach is taken. Basically water is passed through a pipe circuit, part of which runs through the focal points of a set of parabolic mirrors - this heats the water beyond boiling point to produce steam. This in turn drives a turbine to make electricity.

This form of electricity generation is really only suitable for large scale power generation, as the capital and maintenance overheads only it make it worthwhile at large scales.

Solar Hot Water, direct form

This is simply where domestic hot water is run through a form of black coloured radiator on the roof to heat up in the Sun. This hot water is often kept in a water tank fixed to the top of the collector, this allows natural convection to keep reheating the water in the tank and avoids the need for electric pumps.

Solar Hot Water, indirect form

The other option is to use a form of insulated collector to improve the heat transfer. This is most often achieved by having individual 'tubes' with the element to be heated inside a glass tube, so minimizing heat loss. the element is usually made from metal which is then screwed into a head unit, along with all the other tubes, to heat water as it passes over the end of the exposed element.

Although these are more expensive, they do have the advantage of being able to heat the water to a higher temperature for more of the solar year. Their one main disadvantage is that often an electric pump needs to be employed to circulate the water.

For more information on solar hot water heating, see this article.

Air heating

Air heaters simply use the Sun's heat to heat up air passing through them. For instance a solar air heater on the roof could be so configured so that in Summer it 'sucks' hot air out of the house, or in Winter configured so that its hot air is exchanged with the air in the house. These often require some form of fan to operate.

An alternative, little known, is to use something called a Trombe Wall. Basically this an external wall with a sheet of glass over it and an internal vent at the top. This allows hot air under the glass to then get into the internal room whilst at the same time heating the wall to allow stored heat to later make its way into the room also.

For more information on how to use a Trombe Wall, see this article.

Air heating, power generation

A little know technique, and certainly not for the home, is to create a massive Trombe Wall in effect and have at the vent part a wind turbine.

Passive Solar

Passive solar is simply setting up a property so that maximum use of made of the natural solar energy to reduce heating and cooling costs. See this article for more information on how to do it.

Related Books

• Going Solar: Understanding And Using The Warmth In Sunlight
  

  Going Solar contains everything that a budding or experienced solar enthusiast could wish for. By distilling thousands of years of history and knowledge into one book, Tomm Stanley brings together the work of pioneering solar designers, some of the greatest scientists that the world has known and a range of modern, practical applications for hands-on people to create a delicious brew of thought provoking, solar thermal discussion.

  Enthusiastically coaxing readers through the essential concepts at work in fields of study as diverse as history, geography, nuclear physics, thermodynamics and astronomy, Going Solar reveals the "how's" and "why's" behind the solar heating phenomenon. When the subject matter turns to a study of devices that use solar heat, readers have a firm grasp of the natural forces at work and an appreciation of how the technology might be applied in their own lives.

  Written in easy-to-understand language for everyday people and the scientifically challenged, Going Solar contains a delightful blend of humor, fact and function that continually guides readers back to the purpose of its making; understanding and effectively using the warmth found in sunlight for our day-to-day lives.

• Chasing the Sun: Solar Adventures Around the World
  

  If millions of people in the developing world can use solar power, why can't we? The question immediately arises from this fascinating account of the author's 12-year quest to bring solar power and light to people in the developing world who have no electricity.

  Chasing the Sun is a story of dreamers and doers who succeeded in their mission to make the world better by delivering nature's energy to poor people and by building organizations to put the sun at their service in practical, affordable, and effective ways. A green energy development narrative that is fun and eye-opening, the book is also part autobiography. Author Neville Williams' inspiring tale of trailblazing innovation describes:

  His founding the nonprofit Solar Electric Light Fund (SELF) in 1990, which promoted solar power for a decade by setting up pilot solar rural electrification programs in 11 developing countries, including Zimbabwe, India, Nepal, Vietnam, Sri Lanka, and China
  His launching of the commercial Solar Electric Light Company in 1997, which became the SELCO group of companies that has overcome daunting challenges to bring solar electricity to 50,000 families in India, Sri Lanka, and Vietnam

  Filled with colorful characters, the book also features the enthusiasm of maverick devotees to the renewable energy boom of the 1980s and 1990s and their interplay with staid DC-based development institutions, as well as their unique perspective on global solutions to "energy poverty." It will be illuminating to all interested in the environment, development, renewable energy, socially responsible business, and our future at the end of the age of oil.

• The Homeowner's Guide to Renewable Energy: Achieving Energy Independence through Solar, Wind, Biomass and Hydropower (Mother Earth News Wiser Living)
  

  The coming energy crisis caused by a peak in global oil and natural gas production will profoundly affect the lives of all North Americans. As the price of these vital fuels rises, homeowners will scramble to cut their fuel bills. Two options for meeting the upcoming challenge are dramatic improvements in home energy efficiency and efforts to tap into clean, affordable, renewable energy resources to heat and cool homes, to provide hot water and electricity, and even to cook. These measures can result in huge savings and a level of energy independence.

  The Homeowner's Guide to Renewable Energy tells you how. It starts by outlining the likely impacts of fossil fuel shortages and some basic facts about energy. It then discusses energy conservation to slash energy bills and prepare for renewable energy options. Focusing carefully on specific strategies needed to replace specific fuels, the book then examines each practical energy option available to homeowners:

  • Solar hot water, cooking, and water purification
  • Space heat: passive and active solar retrofits
  • Wood heat
  • Passive cooling
  • Solar electricity
  • Wind-generated electricity
  • Electricity from microhydropower sources
  • Emerging technologies-hydrogen, fuel cells, methane digesters,
  • and biodiesel