An Investigation of the Impact of Time of Generation on Carbon Savings from PV Systems in Great Britain

P. A. Burgess
Technologies for Sustainable Built Environments, University of Reading, United Kingdom

M. M. Vahdati
School of Construction Management and Engineering, University of Reading, United Kingdom

D. Davies
Solarcentury, London, United Kingdom

Ladda ner artikelhttp://dx.doi.org/10.3384/ecp110572730

Ingår i: World Renewable Energy Congress - Sweden; 8-13 May; 2011; Linköping; Sweden

Linköping Electronic Conference Proceedings 57:5, s. 2730-2737

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Publicerad: 2011-11-03

ISBN: 978-91-7393-070-3

ISSN: 1650-3686 (tryckt), 1650-3740 (online)


PV only generates electricity during daylight hours and primarily generates over summer. In the UK; the carbon intensity of grid electricity is higher during the daytime and over winter. This work investigates whether the grid electricity displaced by PV is high or low carbon compared to the annual mean carbon intensity using carbon factors at higher temporal resolutions (half-hourly and daily).

UK policy for carbon reporting requires savings to be calculated using the annual mean carbon intensity of grid electricity. This work offers an insight into whether this technique is appropriate.

Using half hourly data on the generating plant supplying the grid from November 2008 to May 2010; carbon factors for grid electricity at half-hourly and daily resolution have been derived using technology specific generation emission factors.

Applying these factors to generation data from PV systems installed on schools; it is possible to assess the variation in the carbon savings from displacing grid electricity with PV generation using carbon factors with different time resolutions.

The data has been analyzed for a period of 363 to 370 days and so cannot account for inter-year variations in the relationship between PV generation and carbon intensity of the electricity grid. This analysis suggests that PV displaces more carbon intensive electricity using half-hourly carbon factors than using daily factors but less compared with annual ones.

A similar methodology could provide useful insights on other variable renewable and demand-side technologies and in other countries where PV performance and grid behavior are different.


Renewable Energy; Photovoltaics; Carbon accounting


[1] DEFRA; Guidance on how to measure and report your greenhouse gas emissions; 2009; pp. 49 - 53

[2] Elexon Portal; Historic Generation By Fuel Type Data Files; https://elexonexchange.bsccentralservices.com/page_object_view.php?uid=76; Accessed online August 2010 (login required)

[3] AMEE; Fuel Emission Factors; http://explorer.amee.com/categories/Electricity_Generation_Emission_Factors/data; accessed online August 2010 (login required)

[4] DECC; Digest of United Kingdom Energy Statistics; 2009

[5] DTI; Future Network Technologies; 2006; pp. 4-5

[6] S. Krauter; Greenhouse Gas Reduction by PV; Proceedings of 3rd World Conference on Photovoltaic Energy Conversion; 2003; pp. 2610 - 2613

[7] R. Laleman et al; Life Cycle Analysis to estimate the environmental impact of residential photovoltaic systems in regions with a low solar irradiation; Renewable and Sustainable Energy Reviews Vol 15; 2011; pp. 267-281 doi: 10.1016/j.rser.2010.09.025.

[8] R. Spiegel et al; Demonstration of the Environmental and Demand-Side Management Benefits of Grid-Connected Photovoltaic Power Systems; Solar Energy Vol. 62; No. 5; 1998; pp. 345–358 doi: 10.1016/S0038-092X(97)00120-5.

[9] G. Keolian and G. Lewis; Modeling the life cycle energy and environmental performance of amorphous silicon BIPV roofing in the US; Renewable Energy 28; 2003; pp. 271–293 doi: 10.1016/S0960-1481(02)00022-8.

[10] A.D. Hawkes; Estimating marginal CO2 emissions rates for national electricity systems; Energy Policy 38; 2010; pp. 5977–5987 doi: 10.1016/j.enpol.2010.05.053.

[11] A. Molin et al; Positive power market value for grid-connected roof-top solar power in Sweden; in Proceedings of the 11th World Renewable Energy Congress (WREC XI); Abu Dhabi; UAE; 25-30 September 2010

[12] S. Gyamfi et al. Demand Response in the Residential Sector: A Critical Feature of Sustainable Electricity Supply in New Zealand; 3rd International Conference on Sustainability Engineering and Science; Auckland; NZ; 2008.

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