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 CO2 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 CO2 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

• Currently 6 gas boilers are used in

the shopping center  Output: 45kW- 220kW  Average Efficiency: 90%  Running Time per Day: 14h

50 100 150 200 250 300 350 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Energy usage 2018 [MWh] Gas usage Heat consumption

• The boilers heat the water to 70°C
• Operate in cascade system
• They are used to cover the demand

for heating, hot water and supply the thermal door curtains

• Gas usage of the boilers in 2018:

1,100 MWh

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

Source: climate-data.org (2018) Source: maps.seai.ie

• Use of geothermal energy for the shopping center is suitable

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
• utput calculation (December 2018)
• The average heat demand per day results from the used heat in

December divided by the running time With: 𝑋

𝐻𝑏𝑡𝐸𝑓𝑑 = 290,000𝑙𝑋ℎ

𝜃𝐶 = 90% 𝑢𝐶𝐸𝑓𝑑 = 14 Τ ℎ 𝑒 ∗ 31𝑒 𝑄𝐼𝐶 = 𝑋

𝐻𝑏𝑡𝐸𝑓𝑑 ∗ 𝜃𝐶

𝑢𝐶𝐸𝑓𝑑 = 620𝑙𝑋

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: 𝜁𝐼𝑄 = 3.5

Source: Viessmann Wärmepumpen

Energy Supply System Analysis- Heat Pump

• In comparison to many other regenerative energy technologies, the heat
• btained 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:
• Finally the electrical input of the heat pump is calculated as follows:

𝑄𝐼𝐼𝑄 = 𝑋

𝐻𝑏𝑡𝐸𝑓𝑑 ∗ 𝜃𝐶

𝑢𝐼𝑄𝐸𝑓𝑑 = 350𝑙𝑋

With: 𝑋

𝐻𝑏𝑡𝐸𝑓𝑑

= 290,000𝑙𝑋ℎ 𝜃𝐶 = 90% 𝑢𝐼𝑄𝐸𝑓𝑑 = 24 Τ ℎ 𝑒 ∗ 31𝑒

With: 𝑄𝐼𝐼𝑄 = 350𝑙𝑋 𝜁𝐼𝑄 = 3.5 𝑄𝐹𝑚𝐼𝑄 = 𝑄𝐼𝐼𝑄 𝜁𝐼𝑄 = 100𝑙𝑋

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:

𝑄𝐹𝑏𝑠𝑢ℎ = 𝜁𝐼𝑄 − 1 ∗ 𝑄𝐹𝑚𝐼𝑄 = 250 𝑙𝑋 With: 𝜁𝐼𝑄 = 3.5 𝑄𝐹𝑚𝐼𝑄 = 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 1600m2

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:

With: 𝑋

𝐻𝑏𝑡𝐶 = 1,100,000 𝑙𝑋ℎ/𝑏

𝑋

𝐻𝑏𝑡𝑄𝑄 = 707,000 𝑙𝑋ℎ/𝑏

𝐺𝑣𝑓𝑚𝐻𝑡 = 𝑋

𝐻𝑏𝑡𝐶 − 𝑋 𝐻𝑏𝑡𝑄𝑄 = 393,000 𝑙𝑋ℎ/𝑏

Emission Savings

• In order to determine the CO2 savings of the alternative system, the resulting

emissions are compared to those of the current plant: 𝑇𝑏𝑤𝑗𝑜𝑕𝑡𝐷𝑃2 = 𝑋

𝐻𝑏𝑡𝐶 ∗ 𝐷𝑃2𝐶 − 𝑋 𝐹𝑚𝑄𝑄 ∗ 𝐷𝑃2𝑄𝑄 = 180,000 𝑙𝑕/𝑏

10 20 30 40 50 60 70 80 90 100 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec CO2 Emissions [tonnes] Emissions Power Plant (Heat Pump) Emissions Boiler Savings

Based on data from 2018

𝑋

𝐻𝑏𝑡𝐶 = 1,100,000 𝑙𝑋ℎ

𝑏 , 𝐷𝑃2𝐶 = 0.3 𝑙𝑕 𝑙𝑋ℎ , 𝑋

𝐹𝑚𝑄𝑄= 280,000 𝑙𝑋ℎ

𝑏 , 𝐷𝑃2𝑄𝑄= 0.5 𝑙𝑕 𝑙𝑋ℎ

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 𝑢𝑄𝐶 = 𝐷𝐸𝑠𝑗𝑚𝑚𝑢𝑝𝑢𝑏𝑚 + 𝑙𝐽𝑜𝑤𝑓𝑡𝑢 ∗ 𝑋

𝐼 + 𝑑𝑁𝑈 ∗ 𝑢𝑏𝐼𝑄

𝐷𝐹𝑜𝑓𝑠𝑕𝑗𝑓𝑢𝑝𝑢𝑏𝑚 = 7𝑏

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
• ptimally 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 CO2 tax
• In the case examined in this study:

 42% CO2 emissions can be saved  35% less required primary energy for heating  57% of the heating costs saved per year

Any Questions?

Thank you for your attention