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Statistics for the System at Neustadt-Glewe and Selected Geothermal Heating Plants

Monthly Fluctuation in Thermal Water Extraction in Neustadt-Glewe in Pure Heat Operation (Year 2000)
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Geothermal Heating Plants in Operation

The geothermal heating plant in Neustadt-Glewe has been in operation since 1995. One important argument in favour of this site was the high aquifer temperature of 100 °C compared with that at Waren and Neubrandenburg. Between 40 and 120 m³ (11-33 l/sec.) are extracted every hour. The salinity of the water is 220 g/l. The glassfibre reinforced epoxy resin pipes showed no evidence of corrosion. After heat recovery, the water is reinjected into the original rock layer at a temperature of 50 °C.

Up to now, the geothermal heat has supplied a modernised district heating net (see Fig. 4) and has a peak output of 11 MW therm, of which 4.5 MW therm is geothermal. A boiler has been integrated to cope with peak demand on cold winter days. So far, the system has supplied an annual average of 90 - 95 per cent of heat demand from geothermal energy. Because of the high temperature of the thermal water, the heating plant operates solely in direct transfer, i.e. without an intermediate heat pump.

Fig. 5 shows the drop in heat demand during the summer months. This cannot be compensated for by supplying heat to industry. Geothermal potential thus remains unexploited during the summer. This influences commercial viability, because up to 40 per cent of the costs involved in a geothermal system stem from drilling alone. At the Neustadt-Glewe facility, operational factors are also an issue. Negative pressure (a partial vacuum) occurs at the injection bore hole as soon as the injection rate falls below 80 m³ per hour. This allows oxygen to enter the system in what is usually a closed thermal water cycle, causing the gases dissolved in the thermal water (proportion: approx. 10%) – largely carbon dioxide, nitrogen and methane – to vaporise off. This is why Neustadt-Glewe is particularly suited to geothermal electricity production.

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Erdwärme-Kraft GbR