GEOTHERMAL SPACE COOLING

Transcription

1 GEOTHERMAL SPACE COOLING 6th African Rift Geothermal Conference ARGeo-C6 Short Course 1 Project Management for Geothermal Development Þorleikur Jóhannesson (Presenter: Yngvi Guðmundsson)

2 Compressor driven chiller Medium capital cost High operating cost High maintenance cost Lifetime ~10 years Uses electricity and cooling water Expected/Typical values Electricity Cooling Water: 27/35 C Chilled Water: 16/6 C Coefficient of Performance: 3-5

3 T-S diagram for R134 - Cooling

4 Water as a refrigerant Why not using water as a refrigerant? To be able to deal with desired temperatures the complete cycle must be under vacuum. Imagine the compressor involved that compresses saturated water vapor from 0,008 bara up to 0,08 bara.

5 T-S Diagram for water

6 Absorption refrigeration The absorption refrigeration cycle becomes attractive when there is an inexpensive heat energy available, like geothermal heat Chiller type Compression Absorption Compression type Mechanical Thermal absorption loop Energy source Electric power Heat energy 85 C 150 C Refrigerant agent Halons, chlorinated CHC, Chlorine free hydrocarbons Water with Lithium bromide as an agent absorption

7 HOW ABSORPTION CHILLER WORKS Working fluid: Water and Lithium Bromide Carrier Fluid: LiBr Refrigerant: Water Non toxic Lithium bromide transported as white odorless salt Easy storage and transport Distilled water used Can be distilled on site

8 Process comparison (Hajime Yabase 2013)

9 Absorption chiller High capital cost ~1,5 2 x compressor driven chiller Low operating cost (geothermal) Low maintenance cost Lifetime 20+ years Expected/Typical values Driving Heat: 95/60 C Cooling Water: 27/35 C Chilled Water: 16/6 C

10 HOT WATER DRIVEN ABSORPTION CHILLER

11 WHY USING GEOTHERMAL FOR COOLING? Compressor systems COP: 5 Mechanical input: Electricity. COP = 2 6 From 1 kwh of electrical energy the cooling machine produces 5 kwh of cooling energy Absorption Chillers COP 1 Thermal input: Geothermal hot water. COP = 0,65-1,2 From 1 kwh of heat input the cooling machine produces 1 kwh of cooling energy Electricity production from heat (geothermal hot water) From 1 kwh of heat a binary power plant produces 0,1 kwh of electricity From 0,1 kwh of electricity a compressor system produces 0,5 kwh of cooling energy Using the geothermal heat will be doubled using it directly, producing chilled water in an absorption chiller, rather than converting it electricity and run compressor chiller!!

12 ECONOMY Brake even with el-compressor system and natural gas absorption heat pump Absorption chiller can break even with the cost of an electric chiller when the: The electric cost is above $0.080/kWh Resource Production of Geothermal water Doublet, 60 kg/s C DT 40 C = 10 MW (Heat) Cost $2 Million $200 / kw (Production price at geothermal field) Equivalent full load power h pr. Year (Abu Dhabi figure) Simple pay back 8 years 200/2850/8 = $ 0,009/kwh Results Drilling for geothermal energy is an attractive option to run absorption Chillers for district cooling systems.

13 District cooling Distribution of chilled water, often around 6 C from a central cooling plant to multiple buildings through a network of pipes for use in space cooling equipment. The heated water is piped back to the cooling plant at 16 C.

14 Main components Cold Sink Wet cooling tower Air cooler Sea water, lake or a river Cooling Plant, product: Chilled water at 6 C Compressor chiller (Electricity) Absorption chiller (Heat) Storage Tanks, Accumulators Cold Water Distribution network, supply and return Consumers Substation HVAC systems in buildings. Forced air ventilation system or free cooling with panels

15 Benefits of district cooling Performance and cost Improved cooling performance Maximized cost effectiveness Minimized capital cost investment for users Space saving Environment Reduced sound pollution in buildings Less environmental impact Geothermal heat pump No oil, gas and almost no electricity CO 2 reduction

16 Efficiency and flexibility Large industrial equipment more efficient than commercial equipment. Flexibility of using different energy sources such as: Electricity Natural gas Waste heat Solar Geothermal energy

17 Inconvenient and drawback Expensive distribution system: often buried pre-insulated piping system Payback is difficult due to low capacity factor Consumers - every house in the district must: 1. Connect 2. Use the system 3. PAY for the use!

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19 Thanks! Normal cooling With district cooling