The future of the energy system will have a dramatic impact on our life and that of coming generations, be it for its impact on climate or on economic growth.
Renewable heating and cooling technology will play a vital role among the available options in the sustainable energy system. This has been identified by the Indian Government as ‘no-regret’ option in its energy roadmap 2030 as it can provide ‘locally produced’ energy. Besides being a decentralised and widely available energy source, it has also an important economic impact: approximately half the investment is allocated to the lower end of the value chain, generating jobs and economic growth at the local level.
Today, about 50% of the final energy demand is used for heating and cooling purposes. Solar thermal energy, together with biomass and geothermal energy, can be a major source of heating and cooling. It is an extremely convenient heating source, based on a simple concept enhanced by cutting edge technology. Thanks to technological progress, solar thermal has become not only a better option for more traditional applications, such as domestic hot water production, but also an attractive alternative for new and more advanced applications such as industrial process heat.
Solar heating and cooling today
Development of solar heating and cooling:
Solar heat can be captured by a variety of technologies and utilised in a wide number of applications. The most mature technology, the solar domestic hot water system.
Two types of solar heater technologies are popular viz., flat plate collectors & evacuated glass tube collectors. Evacuated gas tube solar water heaters are quite popular.
Evacuated tube collectors, where the housing is a glass tube with vacuum inside, so that the heat losses to the environment are very low. Evacuated tube collectors can be classified as direct flow tubes and heat pipe tubes.
However, we have a bad habit of following the technology for years together. Solar water heaters were first deployed in the year 1960 in Australia, Japan and Israel. The same design is being replicated even today in India, even though we have different solar radiation patterns. We have developed nice art of copying the technology as it is without any logic. A typical 125 litres solar water heater commonly used in India is the same as that was few years back. It will be more logical to use heated water up to 700C by 12 noon by transferring to sub-tank (say 20 litres) by a small DC pump to kitchen for number of application for hygienic lifestyle.
Flat plate collector (left) and evacuated tube collector (right)…
Solar air heating systems capture the energy from the sun in an absorbing medium and use it to heat air. Solar air heating systems can also be used in process heat applications, e.g., for crop drying, and in buildings for space heating or air conditioning.
Concentrating solar technologies
Concentrating solar technologies focus sunlight from a large aperture area onto a small area by means of lenses or mirrors. When the concentrated light is converted to heat, very high temperatures can be produced: higher the concentration ratio more is the maximum temperature. So far, high concentrating, sun tracking, solar technologies are mainly used to produce high-temperature heat to drive steam turbines and produce electricity.
However, they can also be used in heat applications; or waste or surplus heat can be utilised in Combined Heat And Power (CHP) installations. Concentrating solar thermal collectors generally need to track the sun (with one or two axis tracking). Only devices with very low concentration can be mounted stationary or with simply seasonal tracking.
Solar cooling technology
Solar cooling technology uses heat in a thermally-driven cooling process. Within solar cooling, there are two main processes: Closed cycles, where thermally driven adsorption chillers produce chilled water for use in space conditioning equipment (air handling units, fan-coils, chilled beams, etc.). Open cycles, also called Desiccant Evaporative Cooling systems (DEC), typically use water as the refrigerant and a desiccant as the sorbent for direct treatment of air in a ventilation system. But, solar cooling is still in the early stages of market development; costs need to be reduced through further development.
Solar heat for cooling applications
An interesting application of solar heat use is building space cooling due to the convenient coincidence between the availability of maximum solar irradiance and the peak demand for cooling, particularly in commercial buildings. Some technologies, like desiccant cooling, can extend comfort by also managing humidity levels. Industrial refrigeration is
also an attractive candidate for solar thermal AC technology.
Solar powered cold chain (warehouse transport, logistics & refrigeration)
The importance of keeping the cold chain cold mainly divided into two sections:
- Solar-powered COLD-CHAIN for effective vaccine management
- Solar-powered cold-chain for effective storage of perishable fruits / food etc.
Peltier-effect based portable vaccine enclosure…
Today, more than 80% of children around the world receive a complete routine of life-saving vaccines during their first year of life.
To a large extent, the evaluation of this decade’s success will be based on the degree to which vaccines reach the people who need them. A strong end-to-end supply chain should adapt to the resource constraints of these communities to ensure that delivery is complete: from the point of production of the vaccine at the manufacturing unit to the point of immunisation.
Solar-powered cold-chain for fruit / vegetables / food…
Vaccines are highly thermo-sensitive biological substances, which have a fixed shelf-life and lose viability over time. The loss of viability is irreversible and accelerated if proper storage and temperature conditions are not maintained. A vaccine vial must remain between 2 and 8 degrees Celsius throughout the entire cold chain system – when it is transported, when it is stored in a refrigerator or cold store, and when it is used at an immunisation session. Solar-powered cold-chain using latest technology plays a major role in this field.
Establishing reliable solar-powered cold-chain for vaccine management for healthy generation all over the world is a challenging task, and is being thought-of & has gathered momentum on ground. Simultaneously, solar-powered COLD-CHAIN to feed the generation the right food / fruits at the right-time at the right-cost is equally important.
Technology for solar-powered cold-chain
Solar-powered cold-chain for vaccine management
A technology based on Peltier-effect is being used all over the world for portable cold-chain vaccine management application, and it is quite successful.
100% Solar-powered cdompressor based cooling or solar – powered heater / chiller technology is commonly used in this field.