Advanced hybrid thermochemical-compression seasonal solar energy storage and heat pump system (Solar S&HP)

太阳能可以提供电力和热能，而不会排放温室气体。一个典型的英国家庭屋顶上的太阳辐射量仍然超过了其全年的供暖需求。然而，目前英国只有1%的可再生太阳能被利用。最重要的原因是供暖需求和太阳能可用性之间的季节性不匹配，以及英国缺乏广泛部署的热能储存。其次，由于远离赤道的太阳辐射相对较弱，使用现有的太阳能集热器获得的热量相对较低，特别是在夏季以外的时期。在这种情况下，必须开发一种季节性太阳能储能系统，在夏季有效地储存大量但温度相对较低的太阳能热量，并在冬季将其用于空间和热水供暖，从而使100%的太阳能部分可用于空间和热水“零碳”供暖。热化学吸附储能技术提供了更高的能量密度和最小的损失，由于温度无关的存储方式，将能量存储为化学势。但其解吸温度（即能量充电过程温度）较高，这使得在英国等高纬度地区使用最成熟、最经济的太阳能集热器技术（平板式或真空管式）回收太阳能存在问题。因此，本项目提出了一种先进的混合热化学吸附和蒸汽压缩工艺，集成电动压缩机，使用少量的电力输入，使大量低温或超低温太阳能热量（<50℃）有效地用于热化学解吸，从而提高太阳能储能和热泵（solar S&HP）的效率、能力和灵活性。由于这种混合系统同时利用热能和电能，当它与太阳能混合热光伏（T-PV）集热器耦合时，这是一个双赢的解决方案。太阳能T/PV集热器为混合储能系统提供太阳能热能和电力，同时从混合太阳能T-PV集热器及时提取太阳能热量也使光伏电池在较低温度下工作，从而提高其电转换效率，从而大大提高整体太阳能转换效率。该系统的其他优点包括：(1)不同能量输入（包括热能和电能）的质量（仅限热能）和数量可以调节，在储存能量的同时相互补充，以应对高度变化的天气条件，同时最大限度地提高太阳能转换。即使没有太阳能发电，也可以利用夏季电网的电力，碳强度比冬季低~15%。(2)混合热化学循环具有较低的解吸温度，减少了储能过程中固体吸附剂和金属反应器的显热损失，进一步提高了储能系统的整体能效。(3)在冬季放热时：(a)可以消除供热的一次能耗，(b)可以在极冷的天气条件下使用热驱动和电驱动热泵过程的集体效应。初步计算结果表明，整个SSTES系统可以提供接近零碳强度的供热，与燃气锅炉和电热泵技术相比，其碳排放量分别降低约92%和85%。

Solar energy can provide both electricity and heat without greenhouse gas emissions. The amount of solar radiation incident on the roof of a typical UK home still exceeds its heating demand over the year. However, there is only 1% of renewable heat from solar currently exploited in the UK. The paramount reason for that is the seasonal mismatch between heating demand and solar thermal energy availability and the lack of extensive deployment of thermal energy storage in the UK. Secondly, because of relatively weak solar radiation being far away from equator leads to relatively low temperature heat using the existing solar thermal collectors, particularly during periods outside summer. In this case, it is imperative to develop a seasonal solar energy storage that can effectively store abundant but relatively low temperature solar heat in summer and utilise this at the desired temperature for space and hot water heating in winter, so that 100% solar fraction can be used for space and hot water 'zero-carbon' heating. Thermochemical sorption energy storage technology offers higher energy density with minimum loss due to the temperature-independent means of storage, storing energy as chemical potential. However, its desorption temperature (i.e. temperature of the energy charging process) is relatively high, which makes it problematic to recover solar energy in high-latitude regions like the UK when using the most mature and economic solar thermal collector technology (flat-plate or evacuated tube type). Therefore, an advanced hybrid thermochemical sorption and vapour compression processes is proposed in this project, the integration of the electric-driven compressor, using a small amount of electricity input, enables a large amount of low or ultra-low temperature solar heat (<50 degC) to be efficiently used for thermochemical desorption, leading to enhance the efficiency, capability and flexibility of solar energy storage and heat pumping (Solar S&HP). Since such a hybrid system utilises thermal energy and electric energy simultaneously, it is a win-win solution when it couples with a solar hybrid thermal-photovoltaic (T-PV) collector. The solar T/PV collector supplies the hybrid storage system with solar heat and electricity, whilst the timely extraction of solar heat from the hybrid solar T-PV collector also allows the PV cell to operate at a lower temperature to increase its electrical conversion efficiency, leading to substantially improved overall solar energy conversion efficiency. Some other detailed advantages of the proposed system are, (1) the quality (thermal only) and quantity of different energy inputs (both thermal and electrical) can be adjusted to complement each other whilst storing energy so as to cope with highly variable weather conditions whilst maximising solar energy conversion. Even if solar electricity is not available, electricity from the grid in summer can be used, which has a ~15% lower carbon intensity than in winter. (2) The hybrid thermochemical cycle has a lower desorption temperature which reduces sensible heat loss from the solid sorbent and metallic reactor during the energy storage process which further increases the overall energy efficiency of storage system. (3) During thermal discharging in winter: (a) primary energy consumption for heating can be eliminated, and (b) the collective effect of thermal-driven and electric-driven heat pump processes can be used in extremely cold weather conditions. The whole SSTES system can provide heating at near zero carbon intensity, its carbon emission is approximately 92% and 85% lower comparing to gas boiler and electric heat pump technology, as revealed by the preliminary calculation results.