Page 213 - Low Temperature Energy Systems with Applications of Renewable Energy

200 Low-Temperature Energy Systems with Applications of Renewable Energy

efficient and compact. Owing to their flexible arrangement, i.e., plates can be removed or
added as needed, these units can be adjusted depending on the geofluid temperature or
heating requirements. They are also easy to disassemble for periodic cleaning.
For more information about greenhouses in the Netherlands, particularly the his-
tory, policies, and regulation of the industry, the reader is referred to Ref. [26].

5.5 Geothermal aquaculture

5.5.1 Introduction

Aquaculture is the practice of raising aquatic species under controlled conditions to
enhance growth and minimize disease. Geothermal aquaculture uses geofluids,
whether taken directly from purpose-drilled wells or tail waters from power production
or direct heating, to maintain uniform temperature and fluid chemistry for optimum
growing conditions.
A guide to the use of geothermal water in the raising of aquatic species may be
found in Ref. [27]; only a summary can be given here. The geothermal fluid must
be of the proper temperature to match the growing needs of the desired species. Where
the geofluid is too hot, as is often the case for waste fluids from power plants, fresh
water is mixed with the geofluid to achieve the desired temperature for the particular
species being raised.
Tilapia is one of the most popular fish for geothermal aquaculture owing to their
love of warm water and tolerance for brackish conditions. Other species that match
up well with geothermal fluids include shrimp, giant prawns, carp, eels, catfish,
sea bass, striped bass, sturgeon, arctic char, salmon, and even crocodiles and
alligators. Oregon in the U.S. is home to several commercial aquaculture operations
including a company called “Gone Fishing” that raises tilapia for sale in large cities
[28].The geofluid is obtained by pumping from wells; the fluid temperature is
82 C.

5.5.2 Case studies: prawn, salmon and arctic char farming

Giant Malaysian prawns grow best in water at 27e30 C and reach maturity in 5e
7months. Geofluids that have been used for space heating are often suitable in tem-
perature to be further used in aquaculture. This is the case at the Oregon Institute of
Technology (OIT) in the U.S. where 56 Cgeofluid leaves the campus district heat-

ing system and flows into ponds where the prawns are raised. A temperature control
system maintains the pond water at 27 C despite very cold winters [29].Many

practical suggestions based on experience can be found in this reference. The
most important fact is that such facilities could not be contemplated in cold climates
without the availability of naturally warm or hot geofluids owing to the economics
involved.
Iceland is one of the leading countries in geothermal aquaculture owing to the abun-
dance of geothermal resources. Figure 5.25 is a schematic flow diagram for one such