An Emissions Arbitrage Algorithm to Improve the Environmental Performance of Domestic PV-Battery Systems

Susan Sun,Richard Wills,Andrew Chipperfield,Andrew Crossland

doi:10.3390/en12030560

Abstract

Domestic PV-battery systems are rarely operated in a way which specifically maximizes environmental benefit. Consequently the studies that seriously examine such systems often find that the greenhouse gas and pollutant emissions savings of rooftop PV, though still positive, are lessened by adding a domestic battery. This study shows thatby simulating a PV-battery system with a range of sizes that this need not be inevitable. A novel algorithm was designed specifically to perform ‘emissions arbitrage’: to charge the battery when the grid emissions intensity is low and to discharge when it is high. It was found that the CO2 saved relative to the same system with PV only can more than pay back the CO2 debt of manufacturing the battery. This is true as long as the UK moves away from the present-day situation where natural gas-fired generators are nearly always the marginal generator. This work underlines the importance of both the operating strategy and the interactions between the system and the entire grid, in order to maximize the environmental benefit achievable with domestic PV-battery systems.

Highlights

There is growing interest in home battery products such as the Tesla PowerWall [1], Moixa Maslow [2], SolarWatt MyReserve [3], BYD B-Box [4], and many others
Kabakian et al (2015) [14] showed that a 1.8 kW PV system with lead-acid batteries in Lebanon had slightly more embodied lifetime greenhouse gas (GHG) emissions than the 1.8 kW PV alone, 92 g of CO2 -equivalent per kWh delivered compared to 89 g/kWh
Using the adapted Hawkes’ method to derive MEF (t) for 2017, different results were found when using the full time series as opposed to the repeated average day’s MEF (t). This shows the importance of using the full time series, as the grid CO2 variation is not adequately represented by an average day, nor is the average day representative of any single real day within the year

Summary

Introduction

There is growing interest in home battery products such as the Tesla PowerWall [1], Moixa Maslow [2], SolarWatt MyReserve [3], BYD B-Box [4], and many others. These complement rooftop solar PV arrays by storing excess generated energy that is not consumed onsite immediately, so that it can be used when consumption exceeds onsite generation. The same was found by Fares and Webber (2017) for Texas [17]

Objectives

Methods

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Discussion

Conclusion