Local Solar Thermal refers to uses of solar energy on a domestic or village scale. Such devices can be built and maintained locally and operated by hand. The basic applications include cooking, heating, baking (food, pottery), and roasting and drying produce. With a bit of development, solar and wood or gas hybrids can bake ceramics, make mortar and cement, reform waste plastics and even work metal. With further development almost all thermal applications can be accomplished directly with the sun.
1. Direct advantages of Local Solar Thermal
A. Sunlight is Universal
Domestic and Local Solar Energy is not a localized phenomenon, but possible for almost everyone. When a distribution network such as DESERTEC is built with a robust development of Local Solar Systems, a stable, feasible, and cost effective energy system emerges for every member of society.
B. Higher efficiency
When solar energy is used directly and locally there is no loss in converting to electricity or some other medium; and so, the cost to accomplish the same thermal task is much less. This decreases the load on the electricity grid and other energy distribution systems. Electricity and other fuels can be more easily be reserved for uses such as electronics, communication, lighting, and motors.
C. Increases stability
Since domestic solar devices need only the sun to operate they are completely autonomous. If there are problems with other sources of energy, such as gas or electricity, it is still possible to do necessary tasks such as cook and boil water with a local solar device. This significantly adds to energy security and stability. Furthermore, if a clean, effective and local alternative to electricity or gas is readily available, it becomes possible for governments to more easily remove conventional energy subsidies (or add taxes) — reducing energy grid loads, pollution, and encouraging development of small scale solar thermal technology and other local energy systems.
D. Fights deforestation
In most non-industrialized places, and even many industrialized places, wood is still a major energy source. This leads to deforestation, habitat loss, land erosion, drought, land slides, and forests that are farther and farther away — requiring more and more labour to go and cut them down.
Most people view forests as one thing, and solar technology as another. However, when we consider that these two have the same source of energy, burning wood becomes simply another solar technology. Which is superior?
When we view trees as solar concentrators, concentrating the sun’s energy into chemical bonds, it becomes instantly clear that they are an extremely poor solar technology. Photosynthesis is at best 10% efficient at converting sunlight into chemical energy. When it comes time to burn this energy, a low quality stove is usually 15-30% and a high quality stove is 50% efficient. So in the best case scenario, where photosynthesis and the stove are the only two factors, burning wood would recover only 2 to 5% of the original solar energy needed to grow the plant, which is already extremely poor. However, in reality there are other losses that are significant such as the energy the plant itself uses to grow, hot spells where less photosynthesis takes place, the
Low Tech Solar Concentration can easily reach over 60% efficiency, and so can save an enormous surface area of trees from being cut down. [1]
To put this in perspective, 3 square meters of plants growing for 1 year could not meet the boiling and cooking energy needs of a single person. A solar concentrator the same size in the sunbelt however receives 3000 peak watts of sun, can easily recover 1800 peak watts, reach over 350 C meeting can work any time there is direct sunlight, meeting the majority of the basic energy needs of more than one person.
2. Indirect advantages of Local Solar Thermal :
A. Easy
A low tech solar device does not need heavy financing or wide political coordination to build and put into place. Most domestic solar devices can be built by any handyman. Low Tech projects are much easier to start and complete. This makes immediate and tangible examples of the potential of solar energy and perhaps the best way to educate the public on the principles and uses of passive and concentrated solar technology in general.
B. Economically accessible
Most people on the planet cannot afford electricity as a primary energy, renewable or not. However, to preserve forests, decrease pollution and increase energy access in poorer regions, an alternative to gas and fuel wood is necessary. In poorer countries, people are unlikely to accept electricity being exported to richer nations if there are energy problems at home. Furthermore, as energy becomes more expensive, even people in industrialized countries will be looking for ways to decrease their energy costs with domestic energy production (solar thermal is already becoming common in the form of passive water heaters, solar concentration may not be far behind).
C. Indefinite Development
Solar Concentration is an incredibly new field. With development, almost all heat applications by humanity can be done by direct solar energy: from making ceramics and cement, to baking silicon computer chips. As the technology develops the low and high tech will start to meet: we shall see more and more commercial and industrial applications in the developing nations, and more and more domestic applications in the industrialized nations. As long as there are stars there is room for development.
3. Obstacles to overcome
A. Circulation of information
The media, governments, and the public are grossly under informed or even misinformed on ecological problems, solar concentration and renewable energy in general. There is a lot of work to be done.
B. Poverty of the Sunbelt Most of the countries that can reap the biggest benefit from solar technology are very poor, and most industrialized nations, which dominate the academic, industrial and financial worlds, are found outside the Sunbelt. This largely explains why solar thermal technology, especially the domestic kind, has been developed very little.
Sunny, rapidly developing economies can lead the way in this sector (and avoid the fossil fuel dependency trap of their mature counterparts). Industrialized northern nations can also invest in this technology for greater world stability, humanitarianism or as part of a carbon credit exchange to offset carbon use.
4. Initial steps
A. Real world centers
Though there is beginning to emerge hubs and networks of information on solar technology on the web, there is a critical lack of technological centers in the real world regrouping small scale solar technologies. If such centers existed it would be easy to compare models and ideas, decrease the reproduction of labour, train people in the methods and technologies, and implement the right technology in the right place.
B. Break the price plain for domestic solar concentrators
As with all new technologies a price plain must be broken before accelerated growth. High capital markets are usually required for the maturing phase of a technology; in this case not only for the concentrators themselves but also applications to make use of the energy they provide. Unfortunately most industrial countries lie outside the Sunbelt. Nevertheless, the industrialized world contains not only sunny places but large numbers of solar enthusiasts, which could support a small market. The next step would be massive diffusion in the rapidly developing economies such as India. Finally, once the technology is mature enough the saturation of the entire Sunbelt is not inconceivable. This would not only alleviate energy poverty but also create new and sustainable economic opportunities for developing economies (since all activity requires energy).
For our own project we are developing a minimalistic kit where the small pieces are shipped by mail, and the larger components of the machine are built on location. We are currently looking for a commercial partner.
C. Government involvement
To quickly tackle deforestation and global warming government investment and involvement is necessary. 5 billion Euros can buy a nuclear power station … or 50 million 2000 watt solar concentrators at 100 Euros each. A single 2000 watt solar concentrator can easily perform the majority of cooking and boiling for 4 people in the Sunbelt (at no fuel cost); which means the basic energy needs of 200 million people. Considering the sun delivers 1000 watts per square meter this is not extraordinary. At such a large scale less than 100 Euros per unit may be realistic.
By Eerik Wissenz June 2008
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