6th November 2018

Erda Impact by Rachel Feeney

Erda Impact

At Erda, we believe in Impact you can measure. On our Erda Impact page we display live data from a small subset of our technology (fig.1 below). This image represents two potential ways of meeting the measured amount of primary heating energy needed by the buildings they are connected to (the pink circle).

Normally – in the UK – natural gas is used to heat our buildings, and the amount of energy it would take a gas boiler system to serve this demand is represented by the black circle. This is always larger than the amount of actual heat you need due to the process of combustion.

Alternatively – the yellow and green circles represent the Erda geo-exchange technology. A combination of energy from the earth and electricity from the UK grid (both of which we have measured). Erda technology can generate the necessary heating for the buildings using a large amount of clean renewable energy from the earth, and a much smaller amount of electricity from the grid.

Fig. 1 The energy impact of heating system choices

The use of energy to meet our buildings heating demands translates into carbon emissions. The carbon impact associated with the choice of heating system can also be viewed on the Erda Impact page. The area in green on the figure represents carbon emissions from Erda technology – using electricity taken from the grid – while the much larger dark-grey area represents carbon emissions from a standard gas boiler.

Fig. 2 The carbon impact of our heating choices


Given that is a data is a small subset of the Erda technology working to reduce energy and carbon in the UK – we wanted to look at the whole of the portfolio to determine the scale of cumulative savings that have come from Erda’s technology.


Energy Performance

To do this we looked back into the data from sites that we have been collecting daily since the systems were turned on and began performing. The Erda | smart™ platform allows us to store and analyse this data.

We record the thermal energy that was generated from these heat pumps for both secondary AHU energy and secondary DHW to determine the total amount of heating energy that each Erda System has generated on a monthly basis. We also recorded the amount of electricity used (from the grid) that our heat pumps and equipment needed to operate. After summing the amount of thermal energy produced from the systems and subtracting the amount of electrical energy from the grid needed to do so, we were able to determine the amount of “free” energy that has been harnessed from the earth, since the time the systems began operating. Further, we determined the amount of energy we saved by using Erda technology to heat the building rather than a gas boiler.


In a typical gas boiler system, the amount of heat generated when burning natural gas is rarely measured, and studies report that the efficiency of this process can vary wildly. To determine the typical amount of primary gas energy that gas boiler systems would need to produce the same measured amount of heating energy, we used the following simple equation:


Thermal demand / 81% = Primary gas energy


This 81% is a standard value used in the boiler displacement method when calculating emissions offset by a CHP plant (2018 Government GHG Conversion Factors for Company Reporting) compared to emissions of a gas boiler.

The figure below approximates the energy Impact Erda technology has made thus far. The green area represents the measured thermal demand of the buildings while the grey represents the estimated amount of primary gas which could have been used to deliver the same heating.

Electricity from the grid (measured) is represented by the orange line on the graph which is the amount of electricity actually used for the Erda technology to meet the same thermal demand.

Fig.3 The Cumulative energy Impact of Erda technology

The difference between the primary gas energy and the electrical energy gives us the amount of energy that Erda systems have saved, 160.84 GWh.


 Carbon Savings

With the energy Impact clear – we wanted to plot what difference our technology has made to the carbon emissions of our heating needs. The carbon emissions associated with natural gas are simple – they are based on a static amount of carbon emitted for kWh of natural gas burnt (which as we know – is not the same as heating energy delivered). Electricity is far more dynamic and it’s carbon content can change every 5 minutes – depending on the generation mix supplying our nation grid.


However – by breaking our measured electrical energy data down individually by month we were able to easily compare it to the average monthly carbon content of the UK grid. Erda currently uses live data from Elexon BMR to calculate the real time carbon intensity for any 5-minute interval on the UK electric grid. We use Elexon BMR instead of sources such as MyGridGB or GridCarbonApp to take a more conservative approach to the calculation of our values. MyGridGB carbon intensity – for example – also estimates the amount of distributed solar energy being generated in the UK, which when added to the overall grid demand would lower the grid carbon values. When calculating our values, the cleaner the electricity looks on the grid at a point in time, the cleaner our technology would appear. By using values from Elexon BMR we only leave room for improvements and “greening” our technology.


The chart below compares the different UK monthly grid carbon intensities from these two sources. The green line representing Elexon BMR (used by Erda Impact) and the blue represents grid figures from MyGridGB.

Fig. 4 Comparative Grid Carbon data sources


We wanted to determine the amount of carbon saved by using the Erda geo-exchange technology to meet heating demands, compared to gas boiler systems. The average monthly UK grid carbon intensity from Elexon BMR was multiplied by the amount of electricity used to determine the monthly CO2 emissions from Erda’s technology.


Erda electricity consumption * CC UK grid = Carbon emitted by Erda System


A gas boiler system has a carbon content of 216 gCO2 per kWh (SAP 2012), we can use that figure to easily calculate the amount of carbon emissions that the gas boiler would have emitted on a monthly basis.


Primary gas energy * 216 = Carbon emitted by gas boiler


The difference in the amount of carbon emitted by the Erda system and the carbon emitted by the gas boiler will provide you with the amount of overall carbon savings from the Erda system thus far.


Carbon emitted by gas boiler- Carbon emitted by Erda system = Overall carbon savings


The chart below summarises the carbon impact Erda technology has made. While the grey area represents the amount of carbon that would have been emitted by the gas boiler if the thermal demand was met through natural gas, the green area represents the amount of carbon that was emitted by meeting the same thermal demand with Erda. The difference between the two areas on the chart is the cumulative amount of CO2 that Erda technology has saved.

Fig. 5 The Cumulative Carbon Impact of Erda technology


 To date, Erda’s geo-exchange technology has saved approximately 28,972 tonnes of carbon and 166.87 GWh of energy. Erda technology has harnessed over 127.3 GWh of free energy from the earth since the systems started operating. These conclusions are based on the cumulative effect of Erda technology with a dynamic and changing UK electrical grid.


We dove even deeper into the data by breaking our carbon savings and energy production into daily and hourly intervals. All the technology has been in full operation since August 2015. Looking at three complete years of operating time (Aug. 15-Aug. 18) we could take the cumulative amount of energy delivered during that time (1080 days) which was a total of 103 GWh and explore ways to meet that same demand.


Erda’s technology meets the demand with 27.53 GWh electricity – we estimated that gas boiler systems would have used 127.6 GWh of gas to deliver the same amount of heat, saving around 100 GWh of energy.

If 103 Gwh of energy were saved in those three years, then that means 20,004 tonnes of CO2 were also saved in that period which breaks down into an average over the last 3 years of 18.52 tonnes of CO2 daily and 0.77 tones of CO2 saved each hour.

In the last 3 years the amount of carbon saved using Erda technology continues to increase annually. From 2016 to 2017 we saw an 11% increase in carbon reduction and the following year saw another increase in carbon savings of 4%. This is because over the last three years the UK grid continues to reduce it’s grid carbon content (shown in fig.4) whilst gas a is a constant figure.


We also wanted to contextualise the Erda Impact in a way which could be more readily visualised – so people can understand the difference we make.


According to SMMT New Car Report and DfT National Travel Survey , the average new UK car in 2017 released 121 gCO2/km and is driven approximately 10,589 km annually. By multiplying the average km’s driven annually by the amount of carbon emitted per km you can conclude that 1,281,269 gCO2 are emitted annually or 1.2 tonnes of CO2 for the average car in the UK. Since Erda systems save approximately 6,761 tonnes of CO2 annually (18.52 tonnes daily), then that is the equivalent of taking an average of 5,634 cars off the road each year.

Erda technology has already hit major milestone savings in both energy and carbon emitted. As the grid continues to green and eventually reach zero carbon, so will Erda’s technology, as its only primary energy source is a small amount of electricity. The future of Erda technology is exciting and the Erda Impact numbers will only continue to grow as the systems continue to operate.


Rachel Feeney
Erda Energy Analyst

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