Former wells for drilling oil and gas could be used to provide geothermal district heating systems by drawing heat from their underground sections.
In a webinar led by geothermal company CeraPhi energy, the company claimed that these redundant wells could be used as a resource to draw heat from deep underground, with the technology already in place to take advantage of district heat.
The webinar, organised by the East of England Energy Group, described taking advantage of existing wells and pipeline infrastructure as an “obvious answer” to helping reduce the climate cost of energy generation.
However, are these resources practical enough on a large scale to provide clean energy?
The Principle
The core principle behind the idea is far from new. In fact, geothermal heat distribution has been used in one form or another since the Paleolithic era.
A district heating system can use pretty much any large source of heat, with the focus of the system being based on distributing this heat around different buildings and houses.
This can also involve a simple boiler station, excess heat from a power plant, solar-generated heat, heat pumps that extract heat from water, as well as waste heat from other processes.
Typically, geothermal has only been taken advantage of in natural heat sources such as hot springs, whilst the principle here is that theoretically anywhere deep enough underground can become a source of geothermal heat.
In theory, this could make it a wholly reliable heat source that can provide energy whenever required, which puts it in stark contrast to wind and solar power.
These two are highly efficient and environmentally friendly energy supplies when they are generating power, however at night solar cannot provide energy and wind turbines require strong but not too strong winds to generate enough power.
The ground can be used as a heat source in the winter and at night, and a heat sink in the summer to keep the pump working at an optimal working temperature.
The key difference with this project compared to other geothermal heat generation is that the aim is to draw heat from wells that have already been drilled and used, rather than drilling from scratch in specific high-temperature heat sources.
This reduces any potential dangers caused by misunderstanding the local geology, which has in the past led to subsidence and in some cases rising of the ground.
This was seen most prominently with a geothermal heating project in Germany that accidentally tapped an aquifer, which caused a chemical reaction that formed expanding gypsum that caused damage to historic buildings in the local vicinity.
The concept uses specialised heat pumps which force heat to transfer from the warm underground into pipe systems, where it can be used directly as a heat source or used to generate electricity.
Used in combination with other sources of electricity such as solar and wind turbines, ground source heat pumps are one of the most environmentally clean, cost-effective and energy-efficient heating systems available, according to the US Environmental Protection Agency.