Solar Thermal Technologies

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Overview

Solar thermal technologies involve harnessing solar energy for thermal energy (heat).

Solar thermal technologies comprise flat or parabollic collectors (low and medium temperatures and high temperature collectors) concentrating sunlight mainly using mirrors and lenses.

Solar Thermal Heating

Solar heating is the utilisation of solar energy to provide process heat, especially in crop drying, water heating, cooking or space heating and cooling. Advanced designs are also used to generate electricity.


Solar Water Heaters (SWH)

Solar collectors are applicable worldwide and are even suitable in areas with low solar radiation and short periods of sunshine.[1] The technology of solar thermal water heaters is present worldwide and significant deployments occur already in emerging economies and developing countries. Technologies include glazed flat plate collectors, evacuated tube collectors, and lower-temperature swimming-pool heaters made from plastic tubes.


Concentrating Solar Thermal Power

Concentrating solar thermal power systems (CSP) use mirrors and tracking systems to focus sunlight from a large area into a small focussed beam. The concentrated heat is then used as a heat source for various applications, such as conventional steam-based power plant, desalination of water, or for cooking. A wide range of concentrating technologies exists; the most developed are the parabolic trough and the solar power tower. Two less well-developed technologies are dish concentrators and linear Fresnel reflectors. Various techniques are used to track the sun and focus light. Very common in CSP is the use of thermal energy storage, which can be used to provide heat at times when the sun is not shining. Energy storage via CSP is cost effective and almost all CSP systems are built with storage capacity up to 15 hours.

Solar cooking can be done are relatively small scale and low cost using a wide range of technologies such as box cookers, solar bowls and the Scheffler reflector


Solar Cooking

Solar cooking allows cooks to heat, cook, bake or pasteurize food or drink. Solar Energy can be an ideal component of the energy mix of a household to complement other combustion-based stoves that can produce heat on demand based on other fuels if the sun does not shine. Local dishes. cooking habits and local climatic conditions determine how much alternative fuels can be saved, around 30%-40%.[2]

Solar Thermal Cooling

Solar thermal energy power stations may also be used for cooling: this refers to either cooling buildings (air conditioning) or industrial processes (refrigeration). Through evaporation and condensation, the solar thermal energy is processed as cold.

There are open and closed systems. Most widely used are closed systems like absorption refrigeration machines and open cooling and dehumidifying processes, such as sorption-supported air conditioning.

The market is at a very early stage, with around 1-2,000 cooling systems have been installed up until 2014. The interest in solar cooling products continues to increase. They are more attractive, in case of high electricity prices and frequent electricity outages. Today, numerous systems from various manufacturers are offered on the market and have reached considerable technical maturity.




Further Information





References

  1. Deutsche Energie-Agentur GmbH (dena), ‘Renewable Energy Solutions for Off-Grid Applications. Providing Electric Power and Heat for Regions without Grid Power or Connected to a Weak Grid’, 2013, http://www.renewables-made-in-germany.com/fileadmin/user_upload/Auslandsmarketing/Offgrid_2013_131020.pdf.
  2. GTZ HERA (2007): Here Comes the Sun. Options for Using Solar Cookers in Developing Countries.