Page 70 - Low Temperature Energy Systems with Applications of Renewable Energy

Characteristics of low-temperature energy sources for heat pumps 59

Fig. 2.9 Schematic of converting ocean thermal energy to electrical power using an organic
working fluid in a closed cycle: 1, warm water feed; 2, evaporator; 3, circulating pump; 4,
turbine; 5, generator; 6, condenser; 7,cold water feed; 8, ocean surface; 9, ocean depths.

creating a partial vacuum, i.e., a vacuum-flash system. Open systems where warm sur-
face waters are used as a working fluid are based upon this principle. Theoretically,
energy conversion systems of the OTEC type could be used not only to produce elec-
tric energy but also to obtain desalinated water.
The transition from experimental research designs to wide industrial acceptance is
challenging because the general biological consequences of raising enormous quanti-
ties of water enriched with biogenic compounds up to warm ocean layers are not
known. But this scientific and technical idea has attracted the attention of scientists,
engineers and funding agencies, such as the U.S. Dept. of Energy, because there are
no theoretical thermodynamic obstacles for successful operation of such systems,
except for the Carnot cycle efficiency that limits such systems to very low thermal ef-
ficiencies. Furthermore, there are many serious practical difficulties to be overcome
which are the subject of several ongoing research and demonstrations [see: https://
en.wikipedia.org/wiki/Ocean_thermal_energy_conversion].

2.4 Industrial water as an energy source for heat pumps

2.4.1 Cooling water discharge from thermal power stations

Despite the modern tendency for decentralization of energy supply sources, many con-
sumers in large cities remain within range of central power stations. Simultaneous pro-
duction of electric power and thermal energy has proven advantages regarding
efficiency of fuel use. That was the motivation for such heat supply systems which jus-
tifies their continued existence; ways to further improve their performance are appro-
priate. When modernizing them technically, first one must take into consideration the
greatest losses of low potential thermal energy in (1) the cooling water system of com-
bined heat and power generating stations (CHPSs), thermal electric stations (TESs)