Solar trough for air-conditioning and process heat
June 18th, 2012 | Technology Times | No Comments
SOLAR TROUGH systems use linear concentrators of parabolic shape with highly reflective surfaces, which can be turned into angular movements towards the sun position and concentrate the radiation onto a long-line receiving absorber tube. The absorbed solar energy is transferred by a working fluid, which is then piped to a conventional power conversion system.
Solar Trough Air Conditioning
Annual average energy consumed by HVAC (Heating, Ventilating, and Air Conditioning) systems contribute to approximately 40 per cent-60 per cent of the total energy use in industrial and commercial establishments. As peak cooling demand runs almost in parallel with peak solar radiation, solar air-conditioning has emerged as an ideal renewable energy solution. CSP technology is an innovative, cost competitive and sustainable solution for solar driven air conditioning – a key technology to offset the effects of fluctuating energy costs while mitigating environmental impacts. Solar air-conditioning also enables major energy savings for large commercial and industrial users, especially for tiered rate structures used by the utilities during peak summer months – offering further cost savings to customers.
The CSP provide solar thermal heat by concentrating the suns energy on a receiver tube and heating the recirculated heat transfer fluid within the system. The generated heat is then used to drive the absorption chiller to provide a renewable source of industrial cooling. Unlike photovoltaic cooling in which PV panels generate solar electricity to power an electrical cooling device, the dual-effect absorption chiller – a refrigeration system that uses a heated thermal fluid to drive a thermo-chemical process – uses water as a refrigerant and lithium bromide (LiBr) as the absorber. Typically, the heated thermal liquid is generated by using a natural gas or a waste heat and fed into the absorption chiller to produce chilled water.
Solar Trough for Process Heat
Industrial heating needs can be categorized into three main temperature ranges. All of them can be achieved with solar. The lowest temperature range consists of everything below 80oC. Solar collectors are capable of meeting these temperatures and are commercially available today. The medium temperature category is between 80oC and 250oC. While the collectors servicing this level of heat demand are relatively limited, they do exist and are on the verge of emerging into competitive commercial production. The highest range includes everything over 250oC and requires concentrated solar power (CSP) to achieve such temperatures.
Average energy use of solar concentrating technologies such as parabolic trough solar collectors has emerged as a cost-competitive solution to replacing natural gas and fuel oil for heating – producing very low levels of greenhouse-gas emissions and proving strong potential in mitigating climate change. CSP parabolic trough technology delivers safe, affordable, and reliable high-temperature process heat for industrial, agricultural or manufacturing processes requiring large volumes of hot water or steam in the range of 93-260 °C. The market for CSP as a renewable solar resource for process heating is particularly promising in rural, agricultural and industrial sectors – including food processing operations where use of steam boilers is prevalent.
According to a study of industrial heating in European countries, 30 percent of industrial processing requires heat below 100oC and 27 percent of industrial heating needs can be met with heat between 100-400oC, and 43 percent requires heat over 400oC. In the food, beverage, transport equipment, textile, machinery, and pulp and paper industries, roughly 60 percent of the heating requirements can be met by temperatures below 250oC. Despite tremendous opportunity, solar thermal heating for industrial processes has been insignificant compared to the residential sector, and the few industrial applications that do exist have been experimental in nature.
• Supplements heat and reduces the load on your usual heating equipment, which can lower maintenance costs and significantly extend the life of the unit.
• Produces emissions-free heat for process heating and offsetting other heating fuels such as propane.
• Decreases the building’s overall energy requirements and ultimately reduces a building’s operating costs.
• Applies to both new and retrofit designs for roofs, free-standing structures, and building re-skinning applications.
• Uses standard plumbing and heating components.
Least Cost Solar Generated Electricity: Trough plants currently provide the lowest cost source of solar generated electricity available. They are backed by considerable valuable operating experience. Troughs will likely continue to be the least-cost solar option for another 5-10 years depending on the rate of development and acceptance of other solar technologies.
Environmental: Trough plants reduce operation of higher-cost, cycling fossil generation that would be needed to meet peak power demands during sunny afternoons at times when the most photochemical smog, which is aggravated by NO emissions from power plants, is produced.
Economic: The construction and operation of trough plants typically have a positive impact on the local economy. A large portion of material during construction can generally be supplied locally. Also trough plants tend to be fairly labor-intensive during both construction and operation, and much of this labor can generally be drawn from local labor markets.
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