A Self-Regulating Heat Pump to Utilize Wind and Wave Energy Sources
Titel:
A Self-Regulating Heat Pump to Utilize Wind and Wave Energy Sources
Auteur:
Pritchard, Colin Low, Robert
Verschenen in:
Energy sources. Part A, Recovery utilization and environmental effects
Paginering:
Jaargang 12 (1990) nr. 1 pagina's 15-24
Jaar:
1990
Inhoud:
Wind and wave energy devices produce their output in the form of shaft work, with a power output which varies over a wide range as the input energy intensity changes. For many processes (desalination, thermochemical processes, steam raising, space heating) energy is required in the form of heat. The conversion of shaft work directly to heat is thermodynamically very inefficient. This efficiency may be greatly improved by using the shaft work to drive a heat pump which abstracts thermal energy from the environment (the sea or airstream) and upgrades it to the requisite temperature level. In this regard, wind and wave energy are ideal sources, since the thermal energy contained in the airstream or sea exceeds by several orders of magnitude the mechanical energy that can be abstracted. Heat pumps have hitherto been designed to utilize a constant work input and a source of heat at variable temperature. But in order to harness renewable energy effectively, a heat pump is required that will utilize variable shaft work to upgrade heat from a source at near-constant temperature. A prototype heat pump is described that enables heat from an ambient source at ∼20°C to be delivered to a load at ∼100°C by a vapor compression system working with variable power input, such as that deriving from wind or wave energy. The design incorporates features that enable power inputs from 0.3-3 kW to be harnessed, corresponding to the wave energy in a0.1-m width of usable wavefront, or the wind energy abstracted by a rotor of 2.5-m diameter in windspeeds of 7-15 m/s. A c.o.p. of ∼3 may be obtained over this range of power input. Thus the heat output is equivalent to that obtainable directly from an energy conversion device of three times the size. The combination of a renewable energy device with a self-regulating heat pump exhibits significant economies of scale up to a unit size of around 1 MW (thermal). Thus the potential uses for this device, particularly in offshore processing and in desalination, are very great.
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