The building sector is responsible for 20% to 40 % of the total energy use, and space cooling or heating are among the biggest energy consumers. Therefore, advancements in cooling or heating technologies play an important role in high-efficiency buildings and low-carbon cities. Heat pumps, including electrically-driven compression cycles and thermally-driven absorption cycles, are widely used for cooling and heating. Although the electrically-driven compression heat pumps are popular due to high efficiencies, the thermally-driven absorption heat pumps are advantageous in solar energy utilisation. However, the absorption heat pumps suffer from some major problems: (1) The intermittence of solar energy requires an auxiliary energy system (e.g., gas boiler or electric heat pump), which degrades the energy saving and increases the investment; (2) The dense urban buildings limit the solar installation space, which leads to low applicability of solar cooling/heating.
To overcome these shortcomings, this invention proposes a novel solar-powered flexible hybrid-energy heat pump, which can gradually transform from an individual thermally-driven absorption heat pump to an individual electrically-driven compression heat pump, with many hybrid cycles of different absorption-to-compression ratios in between. This high flexibility enables the hybrid-energy heat pump to accommodate the time-varying solar radiation, ambient temperature, and building load. Moreover, the integration of refrigerant injection or refrigerant release can reduce the required driving source temperature, which can further increase the solar energy efficiency. This technology provides a novel solution towards energy-efficient, cost-effective, and compact solar cooling/heating.
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TECHNOLOGY FEATURES & SPECIFICATIONS
The combination of an absorption cycle and a compression cycle in the novel hybrid-energy heat pump can strengthen the advantages and cancel the disadvantages of the two cycles.
The compression sub-cycle and the absorption sub-cycle are installed in parallel and share the refrigerant loop (condenser, expansion valve, and evaporator). This internal coupling can simply the system configuration and thus reduce the capital cost.
The integration of refrigerant injection or refrigerant release in the compressor can reduce the required driving source temperature, which is significant for utilising lower-temperature renewable/waste energy that otherwise could not be used. It also enables the novel heat pump to supply space cooling under hotter conditions and space heating under colder conditions, which greatly extends the applicability of solar cooling/heating.
The novel heat-energy heat pump can alternatively operate in various modes depending on the actual situations:
(1) Solar absorption heat pump mode, which is used when the solar radiation is strong and the independent absorption cycle can meet the user load.
(2) Hybrid-energy heat pump mode, which is used when the solar radiation is weak or the user load is high so that the absorption and compression cycles should be activated simultaneously to meet the user load
(3) Electric heat pump mode, which is used when the solar radiation is too weak to power the absorption cycle. Armed with multiple functions, this hybrid-energy heat pump can flexibly accommodate different solar resources, contributing to increased efficiency and applicability of solar cooling/heating.
This novel technology has great potentials for energy savings in a wide range of applications, including cooling, heating, and drying in residential, commercial, and industrial sectors. This novel technology can be used for solar heat pumps and photovoltaic/thermal heat pumps for cooling, heating, and drying applications, with increased solar energy efficiency and minimised solar installation area. In addition, this invention can also be used under extreme weather conditions, including cooling under hotter climates and heating under colder climates, which significantly extends the applicability.
Apart from solar energy utilization, the hybrid-energy heat pump concept is also promising for cooling/heating driven by waste heat and geothermal energy. It can be also used for gas-fired hybrid heat pumps to improve the overall energy efficiency by realising deep heat recovery from the exhaust flue gas. Another important advantage is to make use of lower-temperature heat sources that otherwise could not be used or had to be used with lower efficiencies. Therefore, substantially more renewable energy and waste heat can be efficiently utilized as the driving source of heat pump cycles for cooling, heating, and drying.
This novel technology has great potentials for energy savings and thus cost reduction in a wide range of applications, including cooling, heating, and drying in residential, commercial, and industrial sectors. It can make use of lower-temperature heat sources that otherwise could not be used or had to be used with lower efficiencies. It can be well used to reduce the electricity consumption of cooling/heating and thus decrease the load of power grids.
In summary, this technology provides a novel technology towards energy-efficient, cost-effective, and compact solar cooling/heating. The short-term benefits include energy saving, cost reduction, emission mitigation, while the long-term benefits include low-carbon cities and environmentally-friendly societies.