Solar thermal heating of a glasshouse using phase change material (pcm) thermal storage techniques

Abstract

The Royal Botanic Gardens (RGB) is used as an umbrella name for the institution that runs Kew and Wakehurst Place gardens in Sussex The RBG has a large number of glasshouses at Kew and Wakehurst sites that consume lots of heating energy which is a major concern and the group is looking for an alternative heating system that will be more efficient and sustainable to save energy, cost and reduce CO2 emissions. Glasshouse due to greenhouse effect trap solar energy in the space with the slightest solar gains but the energy trapped in the space most often is vented through the roof wasted to keep the space temperature to the required level. An environmental measurement was carried out in twenty one zones of the glasshouse to establish the temperature and humidity profiles in the zones for at least three weeks. The investigation established that large amount of heat energy is vented to the atmosphere wasted and therefore need a heating system that could absorb and store the waste thermal energy. Phase change material (PCM) thermal energy storage technique was selected to be the best options compared to the others. It has been established that active and passive solar systems could provide enough thermal energy to meet the glasshouse heating requirements. PCM filled heating pipes will be installed to absorb the heat energy trapped in the glasshouse and use it when needed. The research analysis established that 204 MWh of the trapped energy wasted could be saved. The space temperature of the glasshouse could be maintained through melting and freezing of the PCM filled in the heating pipes. The site CHP waste heat could be useful. The research results have shown that nearly zero CO2 emission heating system could be achieved and the project is technically, economically and environmentally viable.