Improving energy efficiency and reducing CO2 emissions from the building

So far, the main way we have lowered the impact of our carbon footprint on climate change has been by reducing carbon dioxide emissions from the building. The sources of carbon emissions are using electricity and gas from the national grid. In our building refurbishment in 2014, we put in green measures to reduce waste in heating and lighting as well as to reduce the import of electricity and gas from the national grid.

  1. Electricity consumption and renewable electricity

Since the building refurbishment, the use of the building by the community increased substantially, particularly at night, with increased demand for heating, lighting and hot drinking water. (Some additional electricity is also required for the operation of the solar panels and ground source heat pump.) Despite having significantly improved the efficiency of the lighting by using LED lighting and microwave sensors controlling the lighting for toilets and corridors, the average annual electricity imported from the national grid increased by about 20% to 13,905 kWh (2015-2019) compared with some 11,275 kWh (in 2012) before the refurbishment.

However, the extra overall demand for electricity was met to some extent by our own renewable energy generation from solar panels. The solar panels produce an annual average of about 9,166 kWh and this substitutes about 40% of what we imported from the national grid in the past.

In addition, our costs for electricity have decreased because the Government’s feed-in-tariff was available when our solar panels were fitted (it has not been available to new schemes since April 2019). The average annual electricity bill we pay for the import from the national grid is £1,964, but the income from the solar panel feed-in-tariff is £1,650, so the net expenditure for electricity is £314.

In a further change to improve our carbon footprint, in 2018 we changed our energy supplier to a 100% renewable energy supplier, Good Energy. Good Energy generates renewable electricity from its own wind and solar farms and buys renewable power from small independent renewable generators. So, although we now import more electricity from the national grid because the building is used more, today, none of the electricity we buy from Good Energy contributes to our building’s carbon footprint.

Annual Average Electricity Consumption and Cost Audit before and after refurbishment
Imported from National Grid (kWh)20122015/2019
 11,27513,905
(cost: £)1,5101,964 (net £314)
Generation by PV (kWh)09,166
(income: £)0£1,650
  1. Gas consumption and renewable heating

The average annual gas consumption after the refurbishment (2015-2019) has been 66,483 kWh, which is less than half the amount of gas used before the redevelopment (151,174 kWh in 2012). This was achieved by replacing an industrial gas boiler with three condensing ones, and a single loop pipe with four loops for the radiators for much more efficient heating. Heating schedules are set weekly and vary depending on which areas of the church building have been booked for use by the church and/or external groups.

In addition, the heating of the newly built room is supplied independently by a ground source heat pump which produced on average 6,548 kWh heat annually (2017-19). The average annual gas bill (2017-19) is £3,238, less than half what we paid before the refurbishment (£7,344 in 2012). We receive a payment of £517 through the Government’s renewable heat incentive (similar to the feed-in-tariff for the solar panels) for the heat produced by the ground pump so that our annual cost for heating is £2,721.

By replacing all single metal framed windows with double glazed ones, as well as cavity wall insulation, the loss of heat from our building has been minimised.

We switched to a 100% renewable supplier, Good Energy, in 2018, and now buy “carbon neutral” gas. What this means in practice is that 10% of Good Energy’s gas is carbon-neutral biogas, produced when organic matter such as leftover food is processed in an anaerobic digester. This is estimated to be the maximum percentage of the UK’s gas demand that can be met sustainably in this way. The other 90% is natural gas, but the carbon emissions are completely neutralised by Good Energy’s investments in verified carbon reduction schemes – mainly biogas schemes in India, China and Turkey.

Annual Average used for Heating / Cooking and Cost Audit before and after refurbishment
Gas Consumption (kWh)20122015/2019
 151,17466,483
(cost: £)20122017/2019

7,3443,238 (net £ 2,721)
Heat generated by heat pump (kWh)06,548
(income: £)0517
  1. The benefit of green measures in the refurbishment in energy use and cost.

By reducing waste and improving the efficiency of energy use, both the amount of energy consumed and the cost for importing energy from national grid were reduced.

Even though we now buy our electricity and gas from a company that supplies 100% renewable energy, we still need to further reduce our use of energy in order to reduce our impact to the environment.

To help monitor how we’re doing, we continue to find it helpful to calculate a “carbon footprint” for energy usage, even though the energy we buy is carbon neutral. To make the comparison between energy consumption before and after using 100% renewable energy more meaningful, we still calculate the carbon footprint based on the amount of energy imported from the national grid.

Annual Energy Audit before and after refurbishment
 20122015/2019
PV electricity production (kWh)NIL9,166
Ground heat production (kWh)NIL6,548
Total energy imported from national grid (kWh)162,44980,388
 20122017/2019
Annual Carbon Footprint based on import of energy (tonnes CO2 emission)27.515.9
Annual Energy Bill (£)8,8515,257 (net 3,131)
  1. Overall energy management and the path toward net zero carbon emissions

Over 20 years, we have been working on energy saving under the programmes of EcoCongregation and EcoChurch.

In the first eight years, we did manage to reduce some electricity consumption by replacing some high power spotlights with condensed florescence ones. In 2012, the electricity consumption was down from 18 mWh (2005) to 11 mWh, a 40% reduction. Similarly, the gas consumption was reduced by turning down the fan speed of the radiators when the rooms were not in use in order to save heating. In 2012, the gas consumption was down from 220 mWh (2005) to 150 mWh, a 30% reduction.

However, the consumption of both gas and electricity was still quite high. The inclusion of energy saving and renewable energy generation in the refurbishment enabled us to reduce gas consumption substantially, to less than 70 mWh. Although we now use more electricity because more people and groups want to use the church premises than before, we are able to meet the Church’s needs, and play our part in the community, with an overall reduction in energy consumption.

Annual electricity imported from national grid (kwh) before and after refurbishment. Supplied by 100% renewable sources.
Annual gas imported from national grid (kwh) before and after refurbishment. Supplied by 100% renewable gas.

The total average annual energy imported from the national grid (2015 – 2019) is 80,388 kWh, less than half of that in 2012 (162,449 kWh) or 35% of that in 2005. We have cut our average annual carbon footprint based on the import of electricity and gas from the national grid by about 40% from 27.5 tonnes CO2 in 2012, or 60% in 2005 to 15.9 tonnes CO2 in 2015 -19.

Annual carbon footprint (tonnes CO2 emission) calculated based on electricity and gas imported from national grid before and after refurbishment. Supplied by 100% renewable sources.

Toward net zero emissions for our building, we may have to consider the following aspects:

  1. The consumption of gas can be reduced by applying a tighter heating schedule and more heat conservation measures.
  1. More electrification to reduce the demand for gas, i.e. replacing the gas oven by an electric one.
  1. Installing a battery to store surplus PV electricity during high production, to use in low production periods. In 2020, the annual PV electricity production was 9.69 MKh but only 39% is used instantly. The total electricity used was 14.56 MWh, 74% of which is still imported from the national grid. While the PV production is higher than demand between April and September, the PV production is well below demand in the other 6 months. Even when a battery is installed, only part of the present import can be covered by PV electricity. Therefore if we want to be completely self-sufficient, with no import from the national grid, the PV system has to be enlarged.