SOLAR TECHNOLOGY

Solar energy is energy from the sun. This energy is in the form of light and heat.

Photovoltaic panels (solar modules) use the sun's light energy to generate electricity. A solar module is made up of multiple cells of semiconductors. When the cells are exposed to light they absorb photons. The individual solar cell is designed with a positive and a negative layer to create an electric field, just like a battery. As photons are absorbed in the cell their energy causes electrons to become free. The electrons move toward the bottom of the cell and exit through the connecting wire. The flow of electrons is what we call electricity.

Solar panels can be very practical in the alpine because they are simple, have no moving parts, and need no maintenance. Photovoltaic cells operate more efficiently in colder temperatures.

Here are the main considerations for effective use of solar power in alpine climates:

• Photovoltaic panels will produce less energy during winter in northern latitudes. It is important to size the system for the appropriate energy demand during the peak season because there are fewer hours of daylight in winter.
• While the conversion efficiency of photovoltaic systems compares favourably to that of small generators, it involves high capital costs and is generally not practical for powering electric resistance heaters.
• Photovoltaic panels should be placed in a location where they won't be shaded by overhanging trees or mountains during certain months of the year. Even partial shading of a solar panel can significantly reduce its power output.
• In order to provide continous power throughout the day and night, electrical energy produced by solar modules must be stored in batteries. Deep cycle sealed batteries are recommended. The efficiency of a battery reduces significantly with declining temperature. Batteries can be damaged if subjected to freezing. This can be prevented by supplying good insulation, a small heat source, or by simply maintaining a high charge rate so that the battery does not regularly deep cycle.

Trends

Ongoing research in photovoltaics promises to increase efficiency and reduce production costs. Optical engineering, nanotechnology, solid-state lighting and low cost organic materials have the greatest potential to make it happen.

Light concentration, by focusing sunlight onto small solar cell areas, can reduce the cost. Micromechanical mirrors and lens systems are the key components for light guidance and concentration on photovoltaic modules. Micro-machined mirror arrays can be used as an alternative to an external rotation mechanism to track the sun position. Nanotechnology research is moving forward to improve photovoltaic conversion of sunlight to power. Photo catalysis and chemical conversions of solar energy will contribute to cost reduction of solar power. SUNRGI declares their PV technology using an X2000 magnification converts 37% of the sunlight directly into electricity by concentrating sunlight onto PV solar cells. This system sends the heat away from the concentration area to keep PV cells cool. The low cost mass production and field installation could result in inexpensive energy production. A production of a commercial product is expected to begin by mid-2009.

Developing cheaper solar cells is at the centre of attempts to make solar electricity cost effective. Designs using inexpensive materials and low cost fabrication methodologies are being investigated at the University of Manchester. Hybrid solar cells have the potential for mass production. The cells are made up of both carbon-based polymeric organic materials and small particles of inorganic materials. Nanotechnology will play a significant role in this investigation.

The development of new thin-film solar cells has reduced the cost of manufacturing. Thin-film PV technologies use considerably less silicon and other materials, so are less expensive to produce. The cells are thin and therefore flexible in nature. The production cost is down to about $1.25 per watt, whereas wafer-based silicon PV modules cost $2.50 per watt. First Solar, a producer of thin-film PV modules, have advertised a goal to achieve 23% of the world market by 2010. New electroplating methods that involve submerging the panels in liquid are less expensive and more environmentally friendly than other methods.

Resources

http://peswiki.com/index.php/Directory:Sunrgi_LLC_Solar_Energy_Systems

http://www.innovations-report.com/html/reports/energy_engineering/report-28607.html

Precedent

Alpine Club of Canada Fay Hut, Kootenay National Park, BC
Solar panels at the Fay Hut provide power to compact fluorescent and LED lights. A solar panel on the outhouse provides a light and runs a ventilation fan for odour control.

The Schiestlhaus, Austria
The Schiestlhaus receives the majority of its energy from a photovoltaic system. It uses a Micro CHP backed up with a rapeseed oil powered generator. Thermal solar collectors integrated with a solid fuel oven are the sources of the hut's heat.
(View the trailer even though it is in German)

Tasmania Cradle Huts
Solar power is used to operate fans for ventilation in the composting toilets.

Solar Thermal

Solar thermal energy is the use of the sun's heat energy. It can be passive or active. Both are based on the greenhouse effect.

Passive solar heating is the absorption of solar energy without the use of pumps, fans or other energy sources. An example is sunlight entering through a large south-facing window and subsequent warming of the inside air, furnishings or specific thermal mass. Another example is passive solar water heaters (most common in regions that do not experience extensive periods of below freezing temperatures).

Active solar thermal incorporates a solar collector that captures the sun's heat energy and transfers it to an air, water or glycol medium by using pumps or fans. This technology is extremely practical for in-floor heating, mass heating or water heating. Examples include Solarwall and domestic hot water heating systems.

Resources

Natural Resources Canada on passive solar heating

Solarwall videos: a) at a Parks Canada building in Winnipeg; b) learn how Solarwall works and is installed

Natural Resources Canada on active solar heating

Solarwall Technology

Solar energy is used to preheat outside air before it is introduced into a building. The warmed air can be distributed as is or further heated in a building's primary heating system. Dark metal cladding, usually unglazed corrugated aluminum, is mounted over a south-facing wall. Sunlight hitting the cladding warms the air near its surface, which is then drawn through thousands of small perforations in the cladding into a narrow space between the wall and the building. The heated air rises to an overhanging canopy plenum, where it is drawn into the facility by fans and dampers. It is simple to install, architecturally aesthetic, requires little maintenance and has a short payback period.

Active Solar Water Heating

Active solar water heaters use pumps to circulate water or a glycol (antifreeze) solution through heat-absorbing solar thermal collectors. In a direct system, the water used by building occupants to bathe or wash their clothes is the same water that is pumped through the solar collector. In an indirect system, an antifreeze solution is pumped through the solar heat collector, which is then used to heat the water used by building occupants.

The techniques required to heat and cool a building passively have been used for thousands of years. Early societies such as the Native American Anasazis and the ancient Greeks perfected designs that effectively exploited these natural processes. The Greeks considered anyone who didn’t use passive solar to heat a home to be a barbarian!