Land Water and Critical Materials Requirements

Land Requirement: As shown in Table 2, the land requirement is assumed to be similar to those for hydrothermal electric systems. It includes the land occupancy for the power plant and surface disturbances due to wells an d pipelines. Roads to the site are not included. The unit land requirements decrease with larger plants.

Water Consumption: Water is required for drilling the deep HDR wells, and for fracturing the HDR reservoi r rock. The amounts required are not quantified here. The system water "makeup" well would be drilled befor e the HDR deep wells are drilled; thus all water needed by the system except for that needed to drill the water well would come from that well.

The power plant is designed with dry cooling towers, so there is no major water consumption by the power plant per se. This is a conscious decision in the system design configuration based on the premise that HDR system s will most likely be developed at arid locations in the western U.S.

Table 2. Resource requirements.

Indicator Name

Current Technology 1997

Units

2020

2030

Net Plant Size

MW

5.06

14.78

29.57

Land Requirement

ha/MW

1.2

.55

.34

ha

6.1

8.1

10.1

Water

Injection Flow Rate

m3/MWh

44.87

40.82

39.93

Estimated Water Consumption

m3/MWh

2.24-6.73

2.04-6.12

1. Water consumption is based on the rate of 5% to 15% of the injection rate.

2. The year 2000-2010 cases are not included in Table 2 because they are all single well triplet plant s similar to the 1997 case

Almost all of the water consumption during system operation will be for water that enters and remains in th e HDR reservoir. Water loss during initial system operation is estimated to be 5% to 15% of the volume pumped through the fracture system [4]. However, these estimates of water loss are based on limited testing of other than commercial-size systems and are uncertain. Actual losses could be more or less depending on the origina l permeability of the reservoir rock. It is estimated by a HDR scientist at Los Alamos National Laboratory that in a commercial system the water loss would become negligible with time [14], on the order of one to two percent of HDR reservoir circulation fow rate.

Energy, Feedstock, and Critical Materials: Electricity is required for startup from cold shutdown. The capacity required is some major fraction of the core-plant cycle parasitic power needs (e.g., for binary fuid circulatio n pumps and cooling fans) plus the power needed to run the HDR-loop high-pressure injection pumps.

Organic or other working fluid is needed to charge the binary power module, and replace small leakage losse s during operation. There are essentially no special materials in these systems.

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