Tag: solar-power

The Road to Carbon-Zero 2024  – First Full Year Fossil-Fuel Free & Battery Upgrade

Introduction

This year marked the first full year where no fossil-fuel was used directly to power and heat the dwelling, and fuel car travel. In November, the electrical energy storage battery was replaced and upgraded to a Tesla Powerwall 3 with 13.5 kWh of storage capacity. This will provide stored off-peak electricity and solar generation to power and heat the home throughout the day, even in mid-winter, and will eliminate grid electricity use in mid-summer. Total emissions were again reduced further and personally controllable emissions remained negative at -0.5 tCO2e, importantly in a year when global carbon emissions were recorded to have risen again according to the UK Met Office. The carbon fingerprint is shown in Fig.1. in comparison with previous years and baseline.

Fig.1. The fingerprint of CO2e emissions in 2024, in comparison with previous years and baseline.

Solar Power Generation

The total solar power generation for the year decreased by 228 kWh to 2155 kWh, derived from reading the generation meters. The primary array data shows that solar irradiance was much lower this year than the 12-year average across the entire year. The monthly solar generation data are shown in Fig.2.

Fig.2. Monthly solar generation data.

Wind Power Generation

The total wind power generation from my ownership share in the Graig Fatha turbine for this year was 4766 kWh, displacing this amount of conventional grid electricity generation with carbon intensity of 0.225 kgCO2e/kWh (DECC, 2024) for a 2024 generation mix. This resulted in an emission off-set of 1072 kgCO2e or 1.1 tCO2e. The monthly wind generation data were derived from my personal Ripple dashboard, and are shown in Fig.3.

Fig.3. Monthly wind power generation data.

Household Electricity Consumption

Total annual household electricity grid consumption was reduced on the previous year by 44 kWh or 4% to 1133 kWh, again derived from reading the electricity meter. Consumption was again well below the six-year average, due mainly to the secondary solar array, but also partly to the reduced storage capacity of the battery during the winter months early in the year. The higher storage capacity of the new battery (pictured in Fig.5.) shows increased consumption in the last two months. The higher-than-average consumption in May, August and September corresponds with the very poor solar irradiance in these three months. The monthly grid electricity consumption data are shown in Fig.4.

Fig.4. Monthly household grid electricity consumption data.

The Tesla Powerwall 3 Electrical Energy Storage Battery has a storage capacity of 13.5 kWh and a power delivery of 11 kW, facilitating coverage of any power use in the property without the use of the grid during peak hours. The system can also work seamlessly in isolation from the grid during a power outage using a gateway. The improved battery chemistry of Lithium Iron Phosphate (LFP) is more sustainable in production, has increased longevity, and can work within greater temperature extremes, and is a significant upgrade.

Fig.5. The 13.5 kWh Tesla Powerwall 3 Electrical Energy Storage Battery and gateway.

The assumption was made that only 25% of solar generation was exported, and 75% was consumed on-site, inferred from monitoring system data. Therefore, 1133 kWh grid consumption minus 539 kWh solar export resulted in a net grid electricity consumption of 594 kWh. Grid electricity was given a carbon intensity figure of 0.225 kgCO2e/kWh (DECC, 2024) for a 2024 generation mix. The combined solar self-consumption and exported generation resulted in emissions remaining stable at 134 kgCO2e or 0.1 tCO2e.

Space and Water Heating

Space heating and water heating was provided by the Mitsubishi Ecodan 5 kW Air-source heat pump (ASHP) for the first full year. The ASHP consumed a total of 2464 kWh of electricity, with 2118 kWh from the grid and the difference supplied by solar power, derived from both a meter and the heating controller, and was given a carbon intensity figure of 0.225 kgCO2e/kWh (DECC, 2024) for a 2024 generation mix. This resulted in 477 kgCO2e or 0.5 tCO2e emissions, approximately half the annual emissions of the gas combi boiler whilst providing more than double the heat and more constant thermal comfort. Importantly, the electrical consumption produced 11056 kWh of heat, giving a coefficient of performance (COP) of 4.01. Essentially, every unit of electrical input delivers 4 units of heat, an efficiency of 400%. For context, a new gas boiler has a real-world efficiency of around 90%, which would only deliver 4675 kWh of heat based on the 10-year average gas consumption in this case. The monthly consumption data is shown in comparison with gas in Fig.6.

Fig.6. Monthly Space & water heating electricity consumption data.

Car Travel

The car in use was a battery electric vehicle (BEV) Hyundai Kona 64-kWh. The annual mileage estimated to the nearest 1000 increased to 13000 miles, or 20500 km. The car was charged in part directly from the solar arrays, and 184 kWh was delivered this way equating to approximately 1200 km. This meant grid consumption was reduced, providing 19300 km of travel. As the fuel is electricity, the carbon intensity figure of fuel production and use in an electric vehicle is the same as is given for grid electricity, which this year was 0.225 kgCO2e/kWh (DECC, 2024) for a 2024 generation mix. The car consumed 2880 kWh of electricity to charge, derived from monthly readings of the night time consumption meter and shown as a column chart in Fig.7., resulting in fuel production emissions only increasing to 615 kgCO2e or 0.6 tCO2e.

Note: In the units previously given for vehicle emissions, 2024 grid electricity equates to 0.03 kgCO2e/km.

Fig.7. Monthly car charging data. (Note: 9-year average excludes 2020 due to pandemic lock-down anomaly).

Water Consumption

Total annual household water consumption increased to 19 m3, derived from a utility bill for that year. The 2024 carbon intensity figure of domestic water supply (0.153 kgCO2e/m3), and treatment (0.186 kgCO2e/m3) is given as 0.339 kgCO2e/m3 (DECC, 2024). This resulted in a 50% increase of 2 kgCO2e to 6 kgCO2e or 0.01 tCO2e emissions. The reason for this increased consumption is not known, and therefore could highlight a potential underground leak or meter issue which is under investigation.

Lifestyle

There were no changes regarding lifestyle in this year, so there was no effect to the results for lifestyle in the carbon footprint calculator (WWF, 2024), and emissions remained at 0.5 tCO2.

Infrastructure

The figure for infrastructure emissions from the carbon footprint calculator remained at 2.75 tCO2 for each UK citizen. The annual donation to the Woodland Trust to plant 25 m2 of woodland, the 14 trees planted, and the green roof and wall off-set and sequester -1.15 tCO2 of these indirect emissions.

Behaviours

There were no behavioural changes in this year, but all previous behavioural changes were maintained. However, the increased storage capacity and power output of the new battery will facilitate more flexibility in electrical power use, for example being able to run several high output appliances at the same time without grid input, if circumstances require it. Previously, this was avoided unless absolutely necessary.

Conclusions

Overall, emissions decreased compared to the previous year by 12% or 0.3 tCO2e, resulting in 79% or 8.5 tCO2e lower annual emissions compared to the baseline year. The ASHP accounted for the decrease, replacing gas for space and water heating, on average halving emissions from this sector. Wind power generation off-set 92% of electricity grid consumption for the home, travel, and space and water heating. This is a great result, considering the share in the wind turbine was matched to provide the consumption of the home and car, but is now also providing most of the heating consumption to.

References

The Department for Energy and Climate Change (2024). Greenhouse gas reporting – Conversion factors 2024. Available at: https://www.gov.uk/government/publications/greenhouse-gas-reporting-conversion-factors-2024 (Accessed 14 January 2025).

WWF, 2025. Footprint Calculator. Available at: https://footprint.wwf.org.uk/ (Accessed 16 January 2025).

The Road to Carbon-Zero 2023  – Electrification of Everything

Introduction

In October this year, an Air-source heat pump was installed, electrifying the space and water heating of the dwelling, and completing the electrification of everything. On November 3rd the gas meter was removed and the supply disconnected. From this moment, the dwelling and travel were 100% fossil-fuel free; net-zero carbon emissions; and net-zero energy bills. In terms of personally controllable emissions, by omitting infrastructure emissions, the value was carbon negative by 0.25 tCO2e. A landmark moment for an average UK dwelling, car mileage, and modern lifestyle. The carbon fingerprint is shown in Fig.1. in comparison with previous years and baseline.

Fig.1. The fingerprint of CO2e emissions in 2023, in comparison with previous years and baseline.

Solar Power Generation

The total solar power generation for the year increased by 422 kWh to 2383 kWh, mainly due to the first full year’s generation from the secondary array, derived from reading the generation meters. The primary array data shows that solar irradiance was lower this year than the 10-year average. The monthly solar generation data are shown in Fig.2.

Fig.2. Monthly solar generation data.

Wind Power Generation

The total wind power generation from my ownership share in the Graig Fatha turbine for this first full year was 4926 kWh, displacing this amount of conventional grid electricity generation with carbon intensity of 0.225 kgCO2e/kWh (DECC, 2023) for a 2023 generation mix. This resulted in an emission off-set of 1108 kgCO2e or 1.1 tCO2e. The monthly wind generation data were derived from my personal Ripple dashboard, and are shown in Fig.3.

Consumer-owned Energy Provider Ripple Energy Referral code worth £25: https://rippleenergy.com?ogu=319&rtrfn=Paul-M

Fig.3. Monthly wind power generation data.

Household Electricity Consumption

Total annual household electricity grid consumption was reduced on the previous year by 23 kWh or 2% to 1177 kWh, again derived from reading the electricity meter. Consumption this year was well below the five-year average, again mainly due to the secondary solar array. The monthly grid electricity consumption data are shown in Fig.4.

Fig.4. Monthly grid electricity consumption data.

The assumption was made that only 25% of solar generation was exported, and 75% was consumed on-site. Therefore, 1177 kWh grid consumption minus 596 kWh solar export resulted in a net grid electricity consumption of 581 kWh. Grid electricity was given a carbon intensity figure of 0.225 kgCO2e/kWh (DECC, 2023) for a 2023 generation mix. The combined solar self-consumption and exported generation resulted in an emission decrease of 19 kgCO2e to 131 kgCO2e or 0.1 tCO2e.

Green Energy Supplier Octopus Energy Referral code worth £50: https://share.octopus.energy/oak-moose-437

Space and Water Heating

Space heating and minimal water heating was provided by the gas grid between January and October. Total annual household gas consumption decreased by 29% on the previous year to 3479 kWh, derived from monthly meter readings, shown as a column chart in Fig.5., and given a carbon intensity figure of 0.2 kgCO2e/kWh (DECC, 2023). This resulted in a decrease of 289kgCO2e to 696 kgCO2e or 0.7 tCO2e emissions.

In the last week of October, the Mitsubishi Ecodan 5 kW Air-source heat pump (ASHP), pictured in Fig.6., was commissioned and began providing all space and water heating electrically for the remainder of the year. The ASHP is assumed to consume all the solar generation which is not exported through the winter months, but is supplied mostly by the electricity grid directly, and indirectly by the battery during peak hours. The ASHP consumed 664 kWh of grid electricity, derived from both a meter and the heating controller, and was given a carbon intensity figure of 0.225 kgCO2e/kWh (DECC, 2023) for a 2023 generation mix. This resulted in 149 kgCO2e or 0.1 tCO2e emissions. The consumption is shown in comparison with gas in Fig.5.

Fig.5. Monthly Space & water heating energy consumption data.

The chart shows how much more efficient the ASHP is, using considerably less energy to provide more heat to the space and water. The house was considerably warmer and more comfortable constantly after the installation. The combination of solar generation, battery storage, and cheap over-night electricity tariff meant the cost was less than gas heating, and these costs were offset by the revenue from the wind turbine and solar Feed-in-Tariff. Net-zero carbon, net-zero cost heating!

Fig.6. The Mitsubishi Ecodan 5 kW Air-source heat pump, located on the side of the property.

Car Travel

The car in use was a battery electric vehicle (BEV). At the end of 2022, the BMW i3 was changed for a Hyundai Kona, pictured in Fig.8. This car is similar in size to the original 100-mile range 24 kWh battery Nissan Leaf, but has a 64 kWh battery providing up to 350 miles of range on a full charge, demonstrating the improvements in battery chemistry and energy density since 2014. The annual mileage estimated to the nearest 1000 remained at 12000 miles, or 19000 km. However, this year the car was able to be charged directly from the solar arrays, and 224 kWh was delivered this way equating to approximately 1500 km. This meant grid consumption was reduced, providing 17,500 km of travel. As the fuel is electricity, the carbon intensity figure of fuel production and use in an electric vehicle is the same as is given for grid electricity, which this year was 0.225 kgCO2e/kWh (DECC, 2023) for a 2023 generation mix. The car consumed 2309 kWh of electricity to charge, derived from monthly readings of the night time consumption meter and shown as a column chart in Fig.6., resulting in fuel production emissions only remaining at 520 kgCO2e or 0.5 tCO2e.

Note: In the units previously given for vehicle emissions, 2023 grid electricity equates to 0.030 kgCO2e/km.

Fig.7. Monthly car charging data. (Note: 8-year average excludes 2020 due to pandemic lock-down anomaly).

Fig.8. The 64 kWh Battery Electric Hyundai Kona.  

Water Consumption

Total annual household water consumption was reduced to 10 m3, derived from a utility bill for that year. The 2022 carbon intensity figure of domestic water supply (0.149 kgCO2e/m3), and treatment (0.272 kgCO2e/m3) is given as 0.421 kgCO2e/m3 (DECC, 2023). This resulted in a 20% reduction of 1 kgCO2e to 4 kgCO2e or 0.0 tCO2e emissions.

Lifestyle

There were no changes regarding lifestyle in this year, so there was no effect to the results for lifestyle in the carbon footprint calculator (WWF, 2023), and emissions remained at 0.5 tCO2.

Infrastructure

The figure for infrastructure emissions in the carbon footprint calculator (WWF, 2023) remained at 2.75 tCO2 for each UK citizen. The annual donation to the Woodland Trust to plant 25 m2 of woodland, the 14 trees planted, and the green roof and wall off-set and sequester -1.15 tCO2 of these indirect emissions.

Behaviours

The addition of the Air-source heat pump required some adjustment to the use of the electrical energy storage (EES) battery. During the winter months, the battery was now charged every night at off-peak rate to discharge and power the heat pump during peak-time periods during the day and evening. It should also be noted that the lead-acid battery after five years of use had, expectedly, reduced in storage capacity by 0.5 kWh. Increased electricity consumption from the heat pump, and reducing battery storage capacity would require a battery upgrade in the next year.

Conclusions

Overall, emissions decreased compared to the previous year by 19% or 0.6 tCO2e, resulting in 77% or 8.2 tCO2e lower emissions compared to the baseline year. A reduction in gas consumption through replacement in the last quarter of the year with the ASHP accounted for 0.3 tCO2e of the decrease. For the second successive year, wind power generation completely off-set all electricity grid consumption for both the home and travel, and this year that included the power consumption of the heat pump for space and water heating, also providing an excess and the remaining 0.3tCO2e reduction through displacing emissions from the National Grid.

References

The Department for Energy and Climate Change (2023). Greenhouse gas reporting – Conversion factors 2023. Available at: Greenhouse gas reporting: conversion factors 2022 – GOV.UK (www.gov.uk) (accessed 17th December 2023).

WWF-UK (2023). Available at: WWF Footprint Calculator (accessed January 2023).