Source Heat Pumps as a Means of Thermal Energy Supply for Large - PowerPoint PPT Presentation

Feasibility Study for Application of Ground Source Heat Pumps as a Means of Thermal Energy Supply for Large Shopping Center Torben Luer Hochschule Bremen City University of Applied Sciences tluer@stud.hs-bremen.de

Structure • General Objectives of the Study • The Mahon Point Shopping Center • Current Heat Supply System • Geothermal Energy in Ireland • Usage of geothermal energy with heat pumps • Energy Supply System Analysis • Ground Source Heat Collector Calculations • Fuel & Emission Savings • Operational Costs and Payback Time • Conclusion

General Objectives of the Study • Reduce green house gas emissions of the Mahon Point Shopping Center • Save fuel and money  Savings for upcoming CO 2 taxes • Positive influence of public perception • Due to the location of the shopping center, geothermal energy is highly suitable  Constant regeneration of heat, all year round  Available 24 h/d (Capacity factor 100%)  In combination with PV, zero CO 2 emissions

Mahon Point Shopping Center • Owner is the Deka Immobilien Investment GmbH • One of Ireland‘s leading shopping centers • On 30 acres, over 60 different shops • About 100,000 visitors per week • Next to the Lake Lough Mahon Source: ocallaghanproperties.com

Current Heat Supply System • • The boilers heat the water to 70 ° C Currently 6 gas boilers are used in • the shopping center Operate in cascade system • They are used to cover the demand  Output: 45kW- 220kW for heating, hot water and supply the  Average Efficiency: 90% thermal door curtains • Gas usage of the boilers in 2018:  Running Time per Day: 14h 1,100 MWh Gas usage Heat consumption 350 Energy usage 2018 [MWh] 300 250 200 150 100 50 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Geothermal Energy in Ireland • Currently very limited in Ireland  Low soil temperatures because of nonexistent volcanic activities (3 K/km to 43 K/km) • Energy at this temperature range can be used to extract low enthalpy energy • Constantly heat regeneration because of water supply  Reduce the risk to cool down the soil • Use of geothermal energy for the shopping center is suitable Source: climate-data.org (2018) Source: maps.seai.ie

Usage of geothermal energy with heat pumps • To extract the geothermal energy of the ground, vertical drillings are used  Average depth: 70m  Expected temperature: 12 ° C (285K) to 15 ° C (288K) • Heat pumps will be used to bring the heat to a higher temperature level  Required electricity will be supplied by the grid or the future PV system • To keep the environmental impact as low as possible, a closed loop borehole heat exchanger (BHE) will be used

Propose energy flow diagram of energy hub in Mahon Point Shopping Center

Energy Supply System Analysis- Boiler • The month with the highest heat demand is used as the reference for the output calculation (December 2018) • The average heat demand per day results from the used heat in December divided by the running time With: 𝑋 𝐻𝑏𝑡 𝐸𝑓𝑑 = 290,000𝑙𝑋ℎ 𝑋 𝐻𝑏𝑡 𝐸𝑓𝑑 ∗ 𝜃 𝐶 𝑄 𝐼 𝐶 = = 620𝑙𝑋 𝜃 𝐶 = 90% 𝑢 𝐶 𝐸𝑓𝑑 Τ 𝑢 𝐶 𝐸𝑓𝑑 = 14 ℎ 𝑒 ∗ 31𝑒

Energy Supply System Analysis- Heat Pump • In order to be able to provide the same output with a heat pump, the coefficient of performance (COP) must first be determined • The COP depends on the temperature difference to be applied between added and outgoing heat  With a minimum difference of 50K: 𝜁 𝐼𝑄 = 3.5 Source: Viessmann Wärmepumpen

Energy Supply System Analysis- Heat Pump • In comparison to many other regenerative energy technologies, the heat obtained by geothermal energy can be called up 24 h/d (Capacity factor 100%) • The required heat output of the heat pump is calculated as follows: 𝑋 𝐻𝑏𝑡 𝐸𝑓𝑑 ∗ 𝜃 𝐶 With: 𝑋 = 290,000𝑙𝑋ℎ 𝐻𝑏𝑡 𝐸𝑓𝑑 𝑄 𝐼 𝐼𝑄 = = 350𝑙𝑋 𝜃 𝐶 = 90% 𝑢 𝐼𝑄 𝐸𝑓𝑑 Τ 𝑢 𝐼𝑄 𝐸𝑓𝑑 = 24 ℎ 𝑒 ∗ 31𝑒 • Finally the electrical input of the heat pump is calculated as follows: 𝑄 𝐹𝑚 𝐼𝑄 = 𝑄 𝐼 𝐼𝑄 With: 𝑄 𝐼 𝐼𝑄 = 350𝑙𝑋 = 100𝑙𝑋 𝜁 𝐼𝑄 𝜁 𝐼𝑄 = 3.5

Ground Source Heat Collector Calculations • To calculate the dimensions of the ground boreholes, it is first necessary to determine the required heat amount that must be extracted from the soil • The following equation was used for the calculation: 𝑄 𝐹𝑏𝑠𝑢ℎ = 𝜁 𝐼𝑄 − 1 ∗ 𝑄 𝐹𝑚 𝐼𝑄 = 250 𝑙𝑋 With: 𝜁 𝐼𝑄 = 3.5 𝑄 𝐹𝑚 𝐼𝑄 = 100 𝑙𝑋 • The neccesary number of boreholes is caculated with:  Drilling depth: 70m  Expected energy yield: 55W/m • The end calculation shows that 65 boreholes are neccesary • In a square shape with a distance of 5m between the holes, about 1600m 2 are needed

Fuel Savings • The electricity for the heat pumps is obtained from the national grid • Public electricity in Ireland is mainly generated by gas fueled power plants  Average efficiency: 30% • The savings result from the difference between the gas used by the boilers and the fuel needed to generate the electricity for the heat pumps in the power plants per year • The fuel savings are calculated as follows: 𝐺𝑣𝑓𝑚 𝐻 𝑡 = 𝑋 𝐻𝑏𝑡 𝐶 − 𝑋 𝐻𝑏𝑡 𝑄𝑄 = 393,000 𝑙𝑋ℎ/𝑏 With: 𝑋 𝐻𝑏𝑡 𝐶 = 1,100,000 𝑙𝑋ℎ/𝑏 𝑋 𝐻𝑏𝑡 𝑄𝑄 = 707,000 𝑙𝑋ℎ/𝑏

Emission Savings • In order to determine the CO 2 savings of the alternative system, the resulting emissions are compared to those of the current plant: 𝑇𝑏𝑤𝑗𝑜𝑕𝑡 𝐷𝑃 2 = 𝑋 𝐻𝑏𝑡 𝐶 ∗ 𝐷𝑃 2 𝐶 − 𝑋 𝐹𝑚 𝑄𝑄 ∗ 𝐷𝑃 2 𝑄𝑄 = 180,000 𝑙𝑕/𝑏 𝐻𝑏𝑡 𝐶 = 1,100,000 𝑙𝑋ℎ , 𝐷𝑃 2 𝐶 = 0.3 𝑙𝑕 𝐹𝑚 𝑄𝑄 = 280,000 𝑙𝑋ℎ 𝑙𝑕 𝑋 𝑙𝑋ℎ , 𝑋 , 𝐷𝑃 2 𝑄𝑄 = 0.5 𝑏 𝑏 𝑙𝑋ℎ 100 Emissions Power Plant (Heat Pump) 90 Emissions Boiler 80 CO 2 Emissions [tonnes] Savings 70 60 50 40 30 20 10 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Based on data from 2018

Operational Costs and Payback Time • In addition to fuel and emission savings, the economic aspects must also be examined • The necessary costs for installation, maintenance, purchase of the installation and energy prices are considered • The calculations showed the following results:  Costs for drilling: 318,000€  Costs for heat pump: 180,000€  Maintenance per year: 2800€  Energy cost savings per year: 70,000€  Payback time: 7 years 𝐷 𝐸𝑠𝑗𝑚𝑚 𝑢𝑝𝑢𝑏𝑚 + 𝑙 𝐽𝑜𝑤𝑓𝑡𝑢 ∗ 𝑋 𝐼 + 𝑑 𝑁𝑈 ∗ 𝑢 𝑏 𝐼𝑄 𝑢 𝑄𝐶 = = 7𝑏 𝐷 𝐹𝑜𝑓𝑠𝑕𝑗𝑓 𝑢𝑝𝑢𝑏𝑚

Conclusion • Due to the location of the shopping center and the prevailing weather conditions, the usage of geothermal energy is particularly suitable • The potential for saving emissions of large building complexes can be optimally utilized • Geothermal energy can be used as low enthalpy energy to cover the heat requirements of large enterprises • Positive image of the shopping center in the public eye • Further savings with a future CO 2 tax • In the case examined in this study:  42% CO 2 emissions can be saved  35% less required primary energy for heating  57% of the heating costs saved per year

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