datarack

 The main food crops harvested for energy are sugar-producing crops (e.g. sugarcane), starch-producing crops (e.g. corn) and oil-producing crops (e.g. rapeseed).[7] Sugarcane is a perennial crop which grows naturally after every crop without replanting, while corn and rapeseed are annual crops. Sugar- and starch-producing crops are used to make bioethanol, and oil-producing crops are used to make biodiesel. USA is the largest producer of bioethanol, while EU is the largest producer of biodiesel.[8] The energy content in the global production of bioethanol and biodiesel is 2.2 and 1.5 EJ per year, respectively.[9] Biofuel from food crops harvested for energy is also called "first-generation" or "traditional" biofuel, and has relatively low emission savings. Perennial energy crops are seen as the "[...] preferred category of crops for energy production [...]" because of high yields and "[...] a (much) better ecological profile than annual crops [...]...

 reservoir reserves heat. thermal engine works between two reservoirs by transferring the heat.. ground source heat pump - very costly to setup. air source heat pump (ASHP) -  vapor-compression refrigeration - for cooling houses and hot water. Air-to-water heat pump - for heating rooms. Electric heat pump water heaters are significantly more efficient than electric resistance water heaters, but also more expensive to purchase. hot engine coolant to heat a vehicle using waste heat from industries and environment. Thermal energy storage (TES) is achieved with widely different technologies. Depending on the specific technology, it allows excess thermal energy to be stored and used hours, days, months later, at scales ranging from the individual process, building, multiuser-building, district, town, or region.