Six ways geothermal can support at-scale electrification in the transition to self-sufficient, affordable and clean energy
Posted on Wednesday, July 20th, 2022
Posted on Wednesday, July 20th, 2022
In our most recent blog series we’ve been discussing how geothermal will hugely impact the decarbonization of heating and cooling. We first explained the systematic approach to the energy transition that initially involves assessing what the critical energy requirement, and then electrifying every energy supply that is possible.
Through combining this approach with innovative business models, we outlined how we could end up using less energy overall, with fossil fuels being replaced by electricity and locally available zero carbon heat like geothermal. Consumers will overall pay less for their energy, and Energy as a Service financial instruments allow customers to avoid having to fund upfront capital costs.
As more and more Renewable Electricity Sources (RES) enter the grid, and/or are supplied locally in micro-grids, so the carbon intensity of the electricity decreases. This proportionately increases the GHG emissions avoidance of the electrified heat compared to the fossil fuel predecessor. In our previous article we illustrated how geothermal resource, the rocks under us, could support integration of these electrical and thermal energy systems through not only providing heat, but by being a repository for heat to store between day and night, summer and winter.
In this article we connect these insights to the needs of the grid electricity providers, as well as end consumers.
Electricity suppliers have the complex task of mapping out demand profiles, understanding seasonal, daily and other variants. In the island of Ireland, for example, the key grid operators, SONI (in Northern Ireland) and EIRGRID (in Ireland), are faced with some tough challenges over the next decade as electricity demand is projected to rise by as much as 30%. At the same time solar and wind generation is also expected to accelerate, while fossil thermal generation which is more predictable “baseload” is set to decline.
On the face of it, electrification of heat with 100,000s of heat pumps will certainly reduce combustion of fossil fuels, but at the same time could place additional burden on the electricity grid. How can the potential downsides of beneficial electrification be managed? We offer six ways in which ubiquitous geothermal resources can today support the electrification mission. Only one of the applications is perhaps restricted in scalability to deployed everywhere. The other five geothermal solutions are doable just about anywhere.
1. Dispatchable geothermal power
One of the biggest challenges of the energy transition is the variability and intermittency of electricity generation by Solar PV and Wind. Battery storage can support grid frequency variation and shorter (hours, minutes, seconds but not days) periods of low wind and solar generation, but the technology is not currently up to providing Long Duration Energy Storage (LDES).
The idea that dispatchable geothermal power can provide clean “baseload” electricity is not new and deservedly is the central thesis of many geothermal power investments. However, the economics of new geothermal developments, outside the traditional geothermal generation regions that are geologically “hot”, are frowned upon because of LCOE outcomes of (much) more than $100/MWh, often substantially more than conventional thermal solutions. But what if we instead compared those economics to the storage alternatives such as battery + wind? Would a low utilization geothermal power scheme make economic sense if the plant was delivering into a high price “peaker” market?
Sadly, the first place to investigate that possibility for geothermal is probably closer to or within the heartland of geothermal power generation today, as the drilling costs to access high temperature resources are today prohibitively expensive in geologically cooler areas of the world, like Ireland and the UK. There is some brilliant work being done by various organizations around the world, particularly in North America, to innovate drilling techniques to reduce the time (and therefore cost) of drilling deep. That technology path needs further investment to accelerate progress and even with that commercial applications are still some years out.
Thankfully there are five other ways for geothermal to support electrification and these can be done most anywhere, now.
2. Ground versus air source heat pumps
The chart above from an article from Jay Egg of Egg Geo LLC a couple of years ago, in which he discussed the various positive aspects of beneficial electrification. It is for a building in Atlanta, Georgia in the southeast United States which enjoys very hot summers and cooler winters. Air source heat pumps (ASHP) are installed for the 1st floor of the building and do a good job of keeping the building cool in the summer, and warm in the winter.
However, the 2nd floor instead uses ground source (or geothermal) heat pumps (GSHP) to provide the same heating and cooling needs. Note how in the summer the efficiency of the GSHP, rejecting heat from the building into the underground, uses about 17% less electrical energy. In the winter, fall and spring the benefits are even larger – more than half of electricity used by the ASHP is needed by the GSHP. This is because the steady underground temperature is that bit higher than the air temperature so the GSHP need less electrical energy to “lift” the heat temperature to the required heating load. Using less electricity for the same thermal load delivered is expressed as a higher Coefficient of Performance (COP) for the geo systems compared to the air source heat pumps.
Note that GSHPs have additional upfront capital costs (drilling the borehole heat exchangers) compared to ASHPs but in this example and many more the operating cost difference through a period of less than 10 years provides sufficient investment return to pay back that upfront capital.
The chart above illustrates how this works through over the life of a project for ground (or geothermal) to be overall less expensive than air source. This analysis used the expected average COP of the two systems in the UK, a different climate from Georgia, over a full year (known as the Seasonal COP, or SCOP). On the left is the total levelised cost for a project of 20 years duration delivering an average 1 MW thermal load deliver by an air source heat pump with a SCOP of 2.1. On the right is the ground source equivalent with a SCOP of 4.1, higher capital costs for geothermal exchange are overwhelmed by the additional electricity costs, even though those are more discounted in levelized calculation.
From the electricity grid perspective, any efficiency improvement is to be welcome as it reduces demand on electricity, in this case in the heat of a deep American south summer. In the modeled UK example, as well as winter and summer peaks reduced, the average electrical demand of the geothermal system is about half of that of the air source.
3. Seasonal storage and improved efficiency
There is a further benefit to ground source geothermal exchangers that is not explicitly illustrated in the Atlanta example above. Heat rejected to the air around an office building or a manufacturing facility is wasted, but heat reinjected in the ground in a geothermal exchange (Underground Thermal Energy Storage) can be recovered again. Hence in summer heat can be stored in the subsurface geothermal resource for retrieval or recycling in the winter. This not only supports the longevity of the geothermal resource, but also substantially improves the overall annual or seasonal efficiency of the system, using 20% to 40% less electricity.
Again, a further benefit not just to the consumer but to the electricity grid company trying to meet demand growth with the minimum investment in their generation and transmission infrastructure.
4. Balancing diverse loads in a microsystem
Where a single facility or microgrid has both heating and cooling loads that run simultaneously for all, or overlap for part of the year there is often a huge opportunity to make the two loads work with one another. However, as we are quickly learning from talking to Causeway Energies customers and working with our B2B partners like Genius Energy Lab and EggGeo LLC, these opportunities are still being often missed by consumers. It seems people tend to think of heating as a combustion problem (most commonly today fossil fuels with their all their issues) and cooling as an electricity problem.
The chart shows the overlap opportunity identified by Stanford University when they began designing their new Combined Heating and Cooling System. The new system was commissioned in 2015 with the expectation that 93% of the campus’s heating and hot water needs could be met by recovering 57% of the waste heat from the chilled water systems. While Stanford does not use geothermal to further couple the loads through seasonal storage, there is the opportunity for other microsystems to do so, hence saving more waste heat from summer cooling for use in the winter when heating dominates.
5. Integrating energy sources and uses in a district
Smart grid concepts, linking together many supplies and uses of electricity in a regional or local system, enables the most efficiency of electrical energy resources. The image above from Egg Geo, LLC, illustrates the how with thinking with smart heat networks can achieve higher efficiencies in thermal energy management. Renewable heat from geothermal, solar thermal and biomass sources can be shared between users. Daily, weekly and seasonal variation can be managed by storage in buffer tanks and deeper borehole heat exchangers. Buildings such as a data centers that generate waste heat can be plumbed into other users of mainly heat such as homes or glasshouses, with seasonal offsets managed through storage.
“Sector coupling” like this can drive efficiency through recycling of thermal energy to the benefit of all consumers and suppliers. The infrastructure that makes it all happen, including the geothermal exchange, becomes a valuable asset to the owners, with multiple revenue streams quickly paying back the upfront capital.
On the supply side, geothermal is similarly the key enabler of thermal energy solutions. A great example of that has been operating for over 10 years in the Drake Landing Solar community in Canada. There the homes are heated with solar thermal energy. The clever integration of geothermal comes through an array of 144 borehole heat exchangers drilled to 35 m depth that stores heat collected from panels on garage rooves during the summer for recovery and home heating in the winter. Note that this system works without heat pumps, so the efficiencies are huge, with all that heat provided using only a small amount of electricity for circulation pumps. There is huge potential to combine geothermal and solar thermal in integrated, efficient systems across many regions in residential, commercial and industrial sectors.
6. Demand side management, both thermal and electrical
As penetration of wind generated electricity into the Irish grid increases, so does the variability of supply due to changes in the weather. This challenge is described as variability when it is predictable or intermittency when it is less so. In Ireland it can occur as too much wind and not enough demand, or too little wind and peak demand not met.
For example, wind turbines are often shut off at night (“dispatched down”) when there is insufficient demand, or the local grid has not the capacity to transmit the load. Hence there are residential schemes to encourage homeowners to use electricity – which will be cheaper – at these times. Heat pumps and thermal storage will be a key part of that solution as will charging of electric vehicles. In industrial and commercial settings Causeway Energies’s Heat as a Service (HaaS) offering has ways of taking advantage of nighttime cheaper electricity.
On the opposite end of the spectrum is when the available electrical generation is insufficient to meet demand. To help meet this challenge, grid operators have in place a demand side management process in which medium to large electricity users Individual Demand Sites (IDS), which have energy components that can either provide electricity into the grid and/or reduce demand by turning or shutting down electrical equipment, are contracted singly or in groups as Demand Side Units (DSUs). The grid operator treats DSUs just like generation capacity. Hence grid operators can manage demand peaks by asking to DSUs to turn down their demand or divert their local generation into the grid. By being available for dispatch the DSU will be eligible for Capacity Payments in the Single Electricity Market (SEM).
Currently DSUs typically have high electrical loads for their manufacturing process and/or have onsite generation such as Combined Heat & Power (CHP) and the flexibility to change their own demand for minutes or hours. As industrial heat is electrified combining locally sourced renewable heat (air, geothermal, solar thermal), the industrial scale heat pumps with their MW-scale electrical demand will qualify for DSU use. Hence Causeway Energies also has that as part of our HaaS customer offer.
We’ve illustrated six ways in which geothermal can support transformation of our electrical and thermal energy systems. We’ve concluded that other renewable energy sources are not competitors in the energy transition. Rather they are allies in the fight against climate change, price volatility of fossil fuels, and energy dependence on foreign oil and gas. The high efficiency of heat pumps, the ability to integrate variable demands and sources of energy, and the “always on” nature and storage capacity of geothermal resources are the principal technology keys to unlock this potential. That’s why Causeway Energies puts geothermal at the core of our energy as a service customer offer.
Get in touch to learn more.
Thanks to Egg Geo LLC and Genius Energy Lab for support in developing this article.