Latent thermal energy storage for solar driven cooling systems
2020
Lebedeva, K., Riga Technical Univ. (Latvia) | Migla, L., Riga Technical Univ. (Latvia)
The paper presents a study based on the transition to a low carbon economy, the targets of at least 27 % of RES, together with the proposed 30 % target on energy efficiency and at least 40 % reduction in greenhouse gas emissions by 2030 will be key drivers in achieving the EU policy goals. According to information provided by the International Energy Agency (IEA), the energy demand for cooling is the fastest growing end-use in the building sector. Sales are rising three times faster than efficiency improvements, and 10 air conditioners will be sold every second over the next 30 years. IEA gives an energy use for space cooling of 3.5 EJ per year and forecasts a more than twice as high demand of 9 EJ per year in 2050. 84 % of heating and cooling is still generated from fossil fuels, while only 16 % is generated from renewable energy. In order to fulfil the EU’s climate and energy goals, the heating and cooling sector must sharply reduce its energy consumption and cut its use of fossil fuels. Solar cooling may have a very positive environmental impact reducing the usage of fossil fuels. The benefit could be evaluated by the avoided amount of CO2 emission, which can reach about 0.5−1.0 kgCO2•kWhE−1 for the grid electricity according to different mixing in electricity production for various countries. Then for every kWh of cooling produced by solar energy, an amount of CO2 that avoided is in the range 160−330 gCO2. In recent years, interest in solar cooling systems has increased in the world and in Europe. Solar Cooling Systems (SCS) are coming solutions to cover the rising demand of air-conditioning. Due to its potential to reduce greenhouse gas emissions, solar driven systems are included in the IEA Solar Heating and Cooling Strategic Plan Key Technologies. The main aim of the paper is to investigate and validate a solar thermal storage tank loaded with 20 cylindrical vertical tubes filled with PCM. The study of a solar thermal driven air-conditioning system with possibility of integration latent heat storage in the cooling system is presented. A simulation model for system dynamical simulations was developed. The PCM melting process and its impact on stable heat maintenance was analysed in deep. It was concluded that using the PCM storage tank, the cooling system COP on average increased comparing COP of SCS without a PCM storage tank. It is concluded that: auxiliary heater turns on times decreased by 21 % compared to usual SCS. The use of latent heat storage technology in the solar cooling system will reduce CO2 emissions by 5−7 %.
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