Servicios No Aeronáuticos Comerciales Facultativos

The use of gas, electricity and DH heat all have environmental impacts including the use of natural resources and the emission of pollutants into the atmosphere during their production. Particulate matter and oxides of nitrogen are of particular concern at a local level in terms of air quality effects while the emission of carbon dioxide and other greenhouse gases to atmosphere has a more dispersed effect. The UK Department of Environment, Food and Rural Affairs (DEFRA) provides organisations with guidance upon measuring and reporting their own greenhouse gas emissions, publishing greenhouse gas emission factors for various types of energy use, including burning fuel as well as for the use of

combined heat and power (DEFRA, 2012). An organisation does not need to separately allocate emissions from CHP to produced heat and power unless some heat or power is sold to another organisation (DEFRA, 2013a).

3.6.1 Emissions from fuel consumption

The emissions factors for various relevant fuels are given in Table 3-10; Scope 1 emissions reflect those emissions of greenhouse gases produced from combustion while Scope 3 includes those associated with extraction, refining and transport of the fuels (Gov.uk, 2013g). For solid biomass, the combustion carbon emissions are assumed to be captured in the plant growth process (in line with EU Renewable

Chapter 3 Theory Energy Directive methodology) and pre-combustion emissions for transport and processing of around 20 kg CO2 equivalent per MWh of thermal content is estimated by DNV GL as applicable (DECC,

2015b); figures for this contribution assessed by the Government are included in Table 3-10.

Table 3-10: Emission factors for fuels. Source: Gov.uk (2013g).

Scope 1 (kgCO2(eq)/kWh) Scope 3 (kgCO2(eq)/kWh) Total emissions (kgCO2(eq)/kWh)

Natural Gas 0.18521 0.01914 0.20435

Fuel Oil 0.26826 0.05059 0.31885

Wood Chips - 0.01579 0.01579

3.6.2 Emissions from heat consumption

The government produces annual average emissions factors for heat and steam supplied via district heating reflecting the national fuel mix but for individual schemes, scheme-specific carbon factors should be used (DEFRA, 2016). In 2012, Sheffield’s city centre district energy system delivered heat with an average carbon intensity factor of 0.137 kg CO2/kWh (ARUP, 2012). The evaluation of the

emissions factors for heat from the district heating system is complicated due to the life cycle assessment of waste disposal and is beyond the scope of this study. The emissions factor for the city- centre network is assumed to be 0.137 kg CO2/kWh and for the Lower Don Valley network the carbon

savings are calculated based on a counterfactual calculated use of gas boilers in the DH network only as the biomass is considered to carry no emissions.

3.6.3 Emissions from distribution losses

For DH-connected businesses, emissions associated with distribution losses are classed as Scope 3 under the GHG Protocol (DEFRA, 2012), and thus need only be included where a company is measuring its Scope 3 emissions. In the UK government methodology, an extra 5% is added to the carbon footprint to allow for typical network losses with DH (ibid.), however in this thesis a specific analysis of the losses is developed.

3.6.4 Emissions from power exchange with the national grid

When power is added to the national grid, the environmental impact can be assessed using the Marginal Emission Factor which represents the emissions factor of the power producer which is required to produce less electricity to balance the system. A study by LCP and Enappsys (2014) looked at the data for the marginal plants in the electricity market over four years and evaluated these marginal emission factors using three distinct approaches. Figure 3-18 shows how the value of marginal emission factor (averaged over all settlement periods) fell to a range of 400-550 kg CO2/MWh in 2013. Further, one of

the calculation methods for marginal plants highlighted that this trend may represent a change from coal to gas as the marginal plant as a result of fuel price movement (LCP and Enappsys, 2014).

Future changes to the MEF were explored in models produced by DECC to understand the impact of bespoke gas CHP policy (DECC, 2014j); these models account for a changing MEF as the UK’s generation mix changes to include increased levels of renewable and low carbon (including carbon capture and storage and nuclear) generation deployment. The MEF for a gas CHP is calculated

depending on whether the CHP responds to retail price signals (for example, a large energy user using CHP to reduce electrical import volumes during high price periods) or in the case of a generator that exports the majority of its output and is influenced by the spot prices then the electricity production pattern will differ.

Figure 3-18: The marginal emission factor for UK grid electricity calculated using three separate methods. Source: LCP and Enappsys (2014).

The projected time series for ‘on-site’ consumption (following retail price signals) and ‘export’ (following wholesale price signals) are shown in Figure 3-19. These MEF projections for ‘on site’ and ‘export’ over future years show initially a greater carbon reduction for on-site electricity consumption due to coal operating at low prices at the electricity generation market; in the future, it is increasingly renewables being curtailed at the margin during low price periods and hence the carbon saving of generation is reduced.

Figure 3-19: Modelled changes to the MEF for gas fired CHP operating under retail and wholesale price signals. Source: DECC (2014j). 0 100 200 300 400 500 600 700 2010 2015 2020 2025 2030 2035 2040 2045 Marginal Emissions Factor (kgCO₂/MWh) Year CHP on-site CHP exporting

Chapter 3 Theory The overall grid emissions factor in future, which reflects the national mixture of electricity generation, is expected to fall as more low-carbon electricity generation capacity is built in the UK. A range of actual and forecast grid carbon intensity factors is given in Table 3-11.

Table 3-11: Forecast and actual grid average carbon intensity factors. Year Value

(gCO2(eq.)/kWh)

Status Notes Source 2012 494 (generation)

43 (losses) 537 total

Actual, grid average factor. DEFRA (2014b). 2013 462 (generation)

38 (losses) 500 total

Actual, grid average factor. DECC (2015g). 2014 412 (generation)

37 (losses) 449 total

Actual, grid average factor. DECC (2016d). 2015 417 (on site)

331 (export)

Forecast, CHP marginal emissions factors.

Onsite CHPs influenced by retail price signals, Exporting CHPs influenced by wholesale prices.

DECC (2014j). 2030 100 Forecast, grid average factor. UK Government expectation. DECC (2014k). 2030 Up to 260 Forecast, grid average factor. Based on possible continued running of

coal plants Gross et al. (2014). 2030 2030 100 200

Forecast, grid average factors. ‘Current Trends’ scenario. ‘Challenging World’ scenario.

DECC (2015b). 2030 312 (on site)

299 (export)

Forecast CHP marginal emissions factor.

Onsite CHPs influenced by retail prices, Exporting CHPs influenced by wholesale prices. DECC (2014j). 2044 229 (on site) 299 (export) Forecast CHP marginal emissions factors.

Onsite CHPs influenced by retail prices, Exporting CHPs influenced by wholesale prices. DECC (2014j). 2050 2050 26 150

Forecast, grid average factors. ‘Current Trends’ scenario. ‘Challenging World’ scenario.

DECC (2015b).

There is a time-lag of two years before the emissions factors are published so 2015’s factors for

comparison will not be available until mid-2017. The relevant carbon factors used in case studies of this thesis are described in Table 3-12. In chapter 5, where the potential for using a heat pump is of

particular interest, three grid average carbon intensity scenarios are considered: 449g, 260g, and 100g CO2(eq.)/kWh, with a pessimistic 260g in 2030 based on the analysis of Gross et al. (2014). The actual

loss factors will vary geographically, the prediction of marginal emissions factor for the CHPs is also dependent on the running pattern, and the presence of some distribution-connected generation means that the exact grid factor will always be subject to some uncertainty.

Table 3-12: Grid carbon emission factors used in each case study.

Application Emissions Factor Approach Applied Factor Used Chapter 4 – CHP use on site 2015 on site CHP predicted marginal emissions factor (417g) with 35g

allowance for losses on avoided import.

417 + 35 = 452g/kWh Chapter 5 – large CHP export

Chapter 5 – heat pump

2015 exporting CHP predicted marginal emissions factor (331g), no losses benefit for exported power.

2014 grid average factors (449g), including losses on power import.

331 g/kWh 449 g/kWh Chapter 6 – large CHP export 2015 exporting CHP predicted marginal emissions factor (331g), no

losses benefit for exported power.