Energy and carbon impact analysis of a solar thermal collector system

Figures & data

Figure 1 A typical active solar heating system with indirect water storage.

Table 1 Property/system requirements.

Property size	Stored water volume (l)	Solar cylinder size (l)	No. of collectors^a
1 bed/1 shower	90	175	1
2 bed/1 bath/1 shower	90	175	1
3 bed/1 bath/2 showers	90/130	175–215	1–2
4 bed/1 bath/2 showers	130/170	215–255	2–3
4 bed/1 bath/3 showers	170	255–305	3
5 bed/2 bath/2 showers	215	305	3
a Area of each collector, 2.03 m^2.

Figure 2 LCCA (based on ISO 14040, 2006).

Figure 3 Four stage LCA methodology (based on ISO 14040, 2006).

Table 2 Materials inventory for the STC. FU is one STC.

Material	Component	Mass (kg)	EE per kg (MJ)^a	Total EE (MJ)	Embodied carbon per kg (kg CO2)^a	Total embodied carbon (kg CO2)
Stainless steel	Absorber	21.28	51.48	1095.49	6.145	130.77
Low-iron glass	Top cover	22.19	13.50	299.53	0.76	16.86
Aluminium	Frame and back plate	10.59	150.20	1590.62	8.35	88.43
Mineral wool	Insulation	3.36	16.60	55.82	1.20	4.04
Total		57.42		3041.46		240.10
^a Source: Bath University ICE-database (Hammond and Jones 2008).

Table 3 Materials inventory for the solar cylinder. FU is one STC.

Material	Component	Mass (kg)	EE per kg (MJ)^a	Total EE (MJ)	Embodied carbon per kg (kg CO2)a	Total embodied carbon (kg CO2)
Copper	Solar storage tank	15.05	70.0	1053.50	5.57	83.83
Polyurethane foam	Storage tank insulation	4.11	72.1	296.01	3.00	12.32
Copper	Boiler coil and solar coil	44.58	70.0	3120.77	5.57	248.32
Total		63.74		4470.28		344.47
^a Source: Bath University ICE-database (Hammond and Jones 2008).

Table 4 Materials inventory for the support and external pipework of the STC. FU is one STC.

Material	Component	Mass (kg)	EE per kg (MJ)^a	Total EE (MJ)	Embodied carbon per kg (kg CO2)^a	Total embodied carbon (kg CO2)
Aluminium	Support of solar collector	4.16	70.0	624.83	5.57	34.74
Copper	Pipework for heat transfer fluid	19.44	72.1	1360.80	3.00	108.28
Total		23.6		1985.63		143.02
a Source: Bath University ICE-database (Hammond and Jones 2008).

Table 5 EE and carbon from the manufacturing phase. FU is one STC.

Component	Primary EE (MJ)	End use EE (MJ)^a	Embodied carbon (kg CO2)^b
Solar collector	176.40	72.32	8.64
Solar cylinder	425.92	74.63	20.88
Support	51.63	21.17	2.53
Total	653.95		32.05
a Based on average fuel efficiency of 41%.
b Based on DEFRA fuel conversion factor of 0.43 kg CO2 per kWh  electricity.

Table 6 EE consumption and CO₂ emissions for various transport means.

Transport method	Energy use	CO2 emission
HGV 50 km	0.19 MJ/kg	0.906 kg CO^2/km
3.5 t Commercial van	4.30 MJ/km	0.272 kg CO^2/km
Average car	3.27 MJ/km	0.204 kg CO^2/km
Sea	0.0003 MJ/km/kg	0.007 kg/tkm
Note: sources Weir (1998) and DEFRA (2008).

Table 7 EE and carbon from transport. FU is one STC.

	Distance (km)	tkm	EE (MJ)	Embodied carbon (kg CO2)
Stage 1	873	52.4	199.00	4.39
Stage 2	40	2.4	0.72	0.02
Stage 3	123	7.38	28.04	0.62
Total			227.8	5.03

Table 8 Distance between London and UK major cities.

Destination	Distance (km)
Edinburgh	660.6
Aberdeen	864.2
Glasgow	648.4
Newcastle	463.5
Liverpool	340.2
Manchester	321.7
Cardiff	243.4
Birmingham	195.2
Oxford	99.9
Bristol	190.8
Brighton	86.7
London^a	20
Population weighted average distance (km)	135.8 km
a Distance travelled within London area included into population weighted average distance.

Table 9 EE and carbon associated with installation and maintenance. FU is one STC.

	EE (MJ)	Embodied carbon (kg CO2)
Installation	584.44	36.94
Maintenance	888.13	55.41

Table 10 Energy and CO₂ emissions from different stages in the life of a STC system for a three-bedroom dwelling incorporating three STCs.

	EE (MJ)	Percentage	CO2 emissions (kg)	Percentage
Installation and Maintenance	1472.57	7.33	92.35	6.46
Transport	683.40	3.40	15.09	0.35
Manufacture	1110.01	5.52	54.39	3.81
Materials	16,829.95	83.75	1277.27	89.38
Total	20,095.93	100	1439.10	100

Table 11 EE and carbon payback periods (in years) for DHW savings of 30–70%: STC system for three-bedroom dwelling incorporating three STCs.

Percentage of total DHW requirement supplied by STC	EE payback (years)^a	Embodied carbon payback (years)
30	6.1	8.2
40	4.6	6.2
50	3.7	4.9
60	3.0	4.1
70	2.6	3.5
a Total EE/carbon of STC system is 20,095.93 MJ/1439.10 kg CO2.

Table 12 Materials inventory for the STC with recycled aluminium and copper, based on the FU of one STC.

Material	Component	Mass (kg)	EE (MJ)	Percentage of energy reduction	Embodied carbon (kg CO2)	Percentage of carbon reduction
Recycled aluminium	STC frame and back plate	10.59	285.93	6.49	17.90	4.90
Recycled copper	Solar storage tank	15.05	752.5	1.50	59.90	4.58
Recycled copper	Boiler coil and solar coil	44.58	2229	4.44	177.43	4.93
Recycled aluminium	Support of solar collector	4.16	112.32	2.55	7.03	1.93
Recycled copper	Pipework for heat transfer fluid	19.44	972	1.93	77.37	2.15
Notes: aluminium: primary EE 150.2 MJ/kg: EC 8.35 kg CO2/kg, recycled EE 27 MJ/kg: EC 1.69 kg CO2/kg (Hammond and Jones 2008); copper: primary EE 70 MJ/kg: EC 5.57 kg CO2/kg, recycled EE 50 MJ/kg: EC 1.69 kg CO2/kg (Hammond and Jones 2008).

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