Dr. Søren Erbs Poulsen (VIA University College), Dr. Theis Raaschou Andersen & Søren Skjold Andersen (Geodrilling)
5GDHC micro grids (Thermonet) in Denmark supported by shallow geothermal energy use
Vejle Fjernvarme
VIA University College
5th generation district heating and cooling (5GDHC)
One grid for both heating and cooling.
Ambient fluid temperatures, uninsulated pipes, zero transmission loss. No fossil fuels or biomass. Free cooling. Seasonal heat storage of fluctuating RE. >70%
geothermal energy for heating. Cooling >
95%. Distributed heat pumps.
Defined by Buffa et al. (2019) who identified 40 grids across Europe An idea ”invented” multiple times in different locations (eg. Ectogrid,
GeoMicroGrid, Thermonet)
Why 5GDHC in DK?
• 34% of the Danish heat consumers are without traditional DH (3GDH)
• No strategic higher level planning of the transition to RE outside 3GDH areas
• Excessive biomass consumption in Denmark
• 3 times more than what is sustainable
• Subsidized and thus disfavoring truly renewable energy sources
• Imported
• We need affordable and clean concepts that are not based on direct use of biomass for
collective heating and cooling supply - first and foremost outside 3GDH areas
3GDH
The future energy supply in Denmark
DK cooling demand 2016:
9.500 GWh (6,8 GW). Equivalent to the annual heating demand of 525,000 family houses.
~50% comfort cooling District cooling in DK:
Societal- og consumer economic benefit of 10 and 13 bio. DKR (1.3 and 1.7 bio. €)
Cooling demand worldwide:
300 til 4.000 TWh from 2000 to 2050. 25%
of the increase due to global warming The Danish Energy Board, 2018 & Køleplan Denmark 2016
Heating Cooling
7 operational 5GDHC grids (Thermonet) in Denmark 4 Thermonet under
construction
Existing grids Future grids
Silkeborg
Existing grids Future grids15 houses (6 kW HP) 6 BHEs, 120 m long Heating but no cooling
DH company owns both grid and HPs.
Standard DH price of heat Practical issues:
- Problems with trapped air (solved)
COP
Annual user costs
3GDH 5GDHC
Tune
Existing grids Future grids3600 m of horizontal uninsulated forward and return piping (Ø40 mm to Ø125 mm)
6 BHEs 200 m (sizing?)
25 terraced and 26 detached houses (51 total) 6 kW and 3 kW Nilan Compact P Geo fully distributed HPs
No cooling (!)
Heat pumps purchased and maintained by house owners. A local energy community owns the grid.
Practical issues:
- Trapped air problem (solved) - Partially distributed heat pumps?
- Choose a heat pump that supports passive cooling (Nibe for instance)
Mageløse (Værløse)
Existing grids Future grids32 houses
6 kW Thermia G3 HP
Energy source: 1 remediation well, 28-30 m3/h
No cooling(!)
Heat pumps purchased by
house owners. Grid financed by house mortgage.
Practical issues:
- Unstable operation due to erroneous installation of HPs - Noise from HPs
- Leakage from grid
• Energy and design models for sizing and estimating capital and operational costs
• Best practise describing all project phases (cook book)
• Viable and optimal business models
• Practical experience and know-how
• Grid source concepts with lower capital costs (than BHEs)
Knowledge gap and R&D projects
Horizontal pipes Vertical drillings (BHE) Energy piles
Geothermal heat exchangers
Cost effective“Design and performance of energy pile foundations”, industrial Ph.d. project
IDEA BASIC RESEARCH
CONCEPTUALIZATION APPLIED RESEARCH SMALL PROTOTYPE LARGE PROTOTYPE SYSTEM PROTOTYPE DEMO SYSTEM FIRST DEMO
FULLY COMMERCIAL
2015 2016 2017 2018 2019 2020 2021 2022 2023
ENERGY PILES
2024
VIA F&U Byggeri, Energi, Vand & Klima
Rosborg Gymnasium
”Design and performance of energy pile foundations”, industrial PhD-project, 2015-2018
VIA University College
• Temperature models and experimental validation
• Dimensioning tool
Optimal number of energy piles and positions
“Design and performance of energy pile foundations”, industrial Ph.d. project
IDEA BASIC RESEARCH
CONCEPTUALIZATION APPLIED RESEARCH SMALL PROTOTYPE LARGE PROTOTYPE SYSTEM PROTOTYPE DEMO SYSTEM FIRST DEMO
FULLY COMMERCIAL “Sustainable, building-integrated
heating and cooling for future resilient cities”, EUDP, 3 mio. DKR
2015 2016 2017 2018 2019 2020 2021 2022 2023
ENERGY PILES
2024
VIA F&U Byggeri, Energi, Vand & Klima
Vejle Fjernvarme
VIA UC
Rosborg Ø
”Sustainable, building-integrated heating and cooling for future resilient cities”
Vejle District Heating VIA University College
• Temperature models and experimental validation
• Dimensioning tool
• Geothermal screening
• 5GDHC computational temperature model
• Business case tool
Soil thermal conductivity s (W/m/K) Volumetric heat capacity s (MJ/m3/K)
Darcy-Weisbach pipe flow model:
h = f ∙ 8L
π2gD5 ∙ Q2; 1
f = c ∙ W e
a bc
bc − a
b 2
Pipe heat transport model:
Soil: Pipe fluid:
𝜕TDs
𝜕tD = 𝜕2TDs
𝜕rD2 + 1
rD
𝜕TDs
𝜕rD ; K1 𝜕TDf
𝜕tD + 𝜕TDf
𝜕zD + K2 TDf − TDs|rD=1 = 0 TDf = ℒ−1 c1e−a1zD
Energy pile heat transport model:
Tf = Tu + Q L
1
2λsGg + RcGc + Rp
Case 1: Office
Case 2: Residential
Geotechnical limit
Geotechnical limit
3 floors, ROI = 3.8 yr
4 floors, ROI = 6.3 yr
The Thermo road combines 5GDHC and SUDS
BHEs
Use existing subsurface infrastructure to remediate symptoms and causes of climate change while
reducing capital costs and area use
Potential bonus: improved water quality
Full scale demonstration!
Tuesday the 13th of October 2020
Tuesday the 20th of October 2020
Tuesday the 27th of October 2020
Tuesday the 3rd of November 2020
Friday the 4th of December 2020
