Optimal GSHP–ASHP hybridisation for large-scale tertiary buildings with imbalanced loads

REFERENCE	LOCATION	CLIMATE	BUILDING	SYSTEM
Pardo et al. (2010)	Valencia (ES)	Mediterranean	Office building	GSHP+ASHP+storage
X. Wang et al. (2010)	Harbin (CN)	Severe cold	Detached house	Solar+GSHP seasonal
You et al. (2014)	3 cities (CN)	Cold	Hotel	GSHP+AHC^a
You et al. (2015)	Harbin (CN)	Severe cold	Hotel	GSHP+AHC^a
Emmi et al. (2017)	Vicenza (IT)	Temperate	Detached house	PVT+GSHP+ASHP
Grossi et al. (2018)	Bologna (IT)	Temperate	Detached house	DSHP^b dual-source
Zheng et al. (2022)	Changsha (CN)	Hot summer	Dormitory	PV+GSHP+ASHP
Li et al. (2024)	Handan (CN)	Cold	Residential complex	PVT+GSHP+ASHP
F. Wang et al. (2024)	Harbin (CN)	Severe cold	Office building	BIPV/T^c+energy piles
Yue et al. (2025)	Qingdao (CN)	Cold	Gymnasium	PVT+GSHP+ASHP+battery

[i] ^aAHC: aerothermal heat compensator. ^bDSHP: dual-source heat pump. cBIPV/T: building-integrated PV/thermal.

Table 2

Performance results and ground temperature drift reported across the ten studies. “ΔT soil” refers to the inter-annual ground temperature change (negative = cooling); values after a slash indicate the stabilised value with the hybrid system active. LCC: life-cycle cost; ALCC: annualised life-cycle cost.

REFERENCE	COP syst.	ΔT soil	ECON. METRIC	KEY FINDING
Pardo et al. (2010)	3.8	N/A	Best payback	Elec. –60% vs ASHP
X. Wang et al. (2010)	6.55	+2 K	–	Solar = 50% of heat
You et al. (2014)	2.9–4.7	–12.7 K/stable	Sav. 5–6%	COP 4.1→2.0 w/o AHC
You et al. (2015)	4.5–15	–11.2 K/stable	Sav. 23.9%	Fails yr 7 w/o AHC
Emmi et al. (2017)	3.55–3.94	–2.5 K (stable)	N/A	PVT+air compet. w/o ground
Grossi et al. (2018)	3.1–3.5	–4.5 K/stable	BHE –30–50%	APF opt. depends on BHE
Zheng et al. (2022)	4.69	–6.3 K/stable	ALCC –8%	COP 3.2→2.9
Li et al. (2024)	3.8–6.0	–1.4 K	ASHP cheaper	Medium-deep 1,500 m
F. Wang et al. (2024)	2.96–3.02	+0.7 K (stable)	LCC –57–62%	Conv. stops yr 11
Yue et al. (2025)	6.3	–2.9 K/+0.1 K	LCC –55%	Elec. –71%

Table 3

Economic parameters for LCOE computation.

PARAMETER	VALUE	UNIT
Drilling cost (equipped borehole)	120	EUR/m
GSHP cost	600	EUR/kW
ASHP cost	600	EUR/kW
Electricity price	230	EUR/MWh
Weighted average cost of capital (WACC)	4	%
Analysis horizon	10	years

System, GSHP and ASHP annual COP as a function of the switching temperature. Dashed curves show the GSHP COP per outdoor air temperature bin (one curve per T_switch); shaded bands indicate the interquartile range. Grey bars represent the normalised heating demand distribution by temperature bin. Top **(a)**: default GSHP performance map. Bottom **(b)**: steep-gradient GSHP performance map.

Monthly-averaged borefield temperature over 25 years for each switching temperature (Langres, 1,000 kW, default performance map). Lower T_switch values preserve the ground temperature by limiting geothermal extraction.

Table 4

Optimal hybrid configurations—Montpellier. For each building (rows) and available surface ratio (column groups), the retained configuration minimises LCOE while satisfying T_fluid ∈ [–3°C, 40°C].

CONFIG.	SURFACE 100%					SURFACE 70%					SURFACE 50%
	$\frac{n}{n_{ref}}$	d	T_SW	COP	LCOE	$\frac{n}{n_{ref}}$	d	T_SW	COP	LCOE	$\frac{n}{n_{ref}}$	d	T_SW	COP	LCOE
	%	m	°C		%ref	%	m	°C		%ref	%	m	°C		%ref
500 kW, 0% HL	70	12.2	8	3.80	92.3	70	10.2	8	3.79	92.3	80	8.0	8	3.80	99.9
500 kW, 20% HL	80	11.2	11	4.74	93.5	80	9.3	10	4.58	95.6	90	7.4	11	4.77	99.9
1000 kW, 0% HL	80	11.2	11	4.47	90.8	70	10.0	8	3.81	90.8	80	7.9	8	3.81	97.8
1000 kW, 20% HL	80	11.2	11	4.76	93.0	80	9.3	10	4.59	95.1	80	7.9	8	4.13	100.8
2000 kW, 0% HL	70	12.0	8	3.82	91.1	70	10.0	8	3.82	91.1	80	7.9	8	3.82	98.3
2000 kW, 20% HL	80	11.2	10	4.60	95.4	80	9.4	8	4.14	101.1	80	7.9	8	4.15	101.1

[i] n/n_ref: borehole count vs. reference; d: borehole spacing; T_sw: switching temperature; COP: global system COP (heating + cooling); LCOE: relative to reference geothermal installation (100% = same cost). HL: cooling-to-heating load ratio.

Table 5

Optimal hybrid configurations—Langres. Same conventions as Table 4.

CONFIG.	SURFACE 100%					SURFACE 70%					SURFACE 50%
	$\frac{n}{n_{ref}}$	d	T_SW	COP	LCOE	$\frac{n}{n_{ref}}$	d	T_SW	COP	LCOE	$\frac{n}{n_{ref}}$	d	T_SW	COP	LCOE
	%	m	°C		%ref	%	m	°C		%ref	%	m	°C		%ref
500 kW, 0% HL	70	11.9	6	3.46	85.2	70	10.0	4	3.13	89.2	80	7.9	4	3.13	96.3
500 kW, 20% HL	70	11.9	6	3.85	88.2	70	10.0	4	3.51	92.8	80	7.9	6	3.87	94.3
1000 kW, 0% HL	70	12.0	6	3.46	85.7	70	10.0	4	3.14	89.5	80	7.9	4	3.14	96.8
1000 kW, 20% HL	70	12.0	6	3.86	88.8	70	10.0	4	3.54	93.2	80	7.9	4	3.55	100.1
2000 kW, 0% HL	70	12.0	7	3.64	83.5	70	10.0	4	3.17	88.6	80	7.9	4	3.17	96.4
2000 kW, 20% HL	70	12.0	7	3.92	85.0	70	10.0	6	3.77	86.6	80	7.9	6	3.77	94.1

Effect of GSHP rated extraction intensity on 10-year average energy yield and geothermal coverage (Montpellier, 1,000 kW, 60% cooling ratio, 20 boreholes at 200 m).

Annual performance degradation of the base-load hybrid system (Langres, 1,000 kW, heating only, 20 boreholes at 200 m). Top: energy yield (bars) and geothermal heat share (line). Bottom: mean borefield temperature.

Table 6

Base-load hybrid system performance (10-year average, 1,000 kW, 20 boreholes at 200 m). The ref row gives the GSHP-only reference for direct comparison. HL: cooling-to-heating load ratio; d: borehole spacing; yield: energy delivered per metre of borehole per year; f_h, f_c: geothermal heating and cooling coverage.

CONFIGURATION	d(m)	YIELD kWh/m/yr	COP syst.	f_h(%)	f_c (%)	LCOE EUR/MWh
Montpellier (GSHP 80 W/m = 320 kW)
0% HL, ref	10	42	4.84	100	–	352
0% HL, hybrid	12	149	3.65	54	–	208
0% HL, hybrid	8	120	3.51	44	–	210
20% HL, ref	10	61	4.93	100	100	281
20% HL, hybrid	12	207	3.94	61	71	180
20% HL, hybrid	8	188	3.86	54	71	181
60% HL, ref	10	92	5.02	100	100	233
60% hybrid	12	289	4.20	70	58	147
60% HL, hybrid	8	286	4.19	68	60	147
Langres (GSHP 200 kW)
0% HL, ref	10	37	4.11	100	–	364
0% HL, hybrid	12	128	2.81	32	–	176
0% HL, hybrid	8	93	2.72	23	–	178
20% HL, ref	10	58	4.32	100	100	279
20% HL, hybrid	12	219	3.21	42	61	151
20% HL, hybrid	8	195	3.15	36	61	152

Articles in this issue

DOI: https://doi.org/10.66506/essp.8-017-26 | Journal eISSN: 2001-7960

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Language: English

Page range: 53 - 53

Submitted on: Mar 19, 2026

Accepted on: May 8, 2026

Published on: Aug 31, 2026

Published by: European Council for an Energy Efficient Economy (eceee)

In partnership with: Paradigm Publishing Services

Keywords:

hybrid ground-source heat pump,

borehole heat exchanger,

TRNSYS simulation,

borefield optimisation,

fluid temperature constraints,

LCOE,

geothermal energy

© 2026 Hugo Marchand, Chloé Duchayne, published by European Council for an Energy Efficient Economy (eceee)
This work is licensed under the Creative Commons Attribution 4.0 License.

Volume 1 (2026): Issue 1

Optimal GSHP–ASHP hybridisation for large-scale tertiary buildings with imbalanced loads

Figures & Tables

Table 1

Table 2

Table 3

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Figure 2

Table 4

Table 5

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Figure 4

Table 6

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