The groundwater heating System
Groundwater heating or geothermal heating can help us in our struggle to avoid extremely high energy bills! So let’s have a look at groundwater heating for heating or cooling our houses. Increasing energy prices may not be the only reason to look for different technologies. Our houses and all the other buildings are responsible for almost half the world’s Carbon Dioxide. So these are two very important reasons to look for Low- and Zero-Carbon energy systems (LZC).
Next to the more commonly known LZC systems like solar and wind power, there is a much more reliable power source to manage our home-temperature: groundwater heating. One of the big advantages of groundwater heating is that it is very reliable. Different from solar- or wind-energy no wind or sun is needed. The temperature in the used source is very stable. So in our search for renewable energy and a Livin’ Green Lifestyle, groundwater heating is very interesting.
How does groundwater heating Work?
Explanation of the groundwater heating systems
The most common groundwater heating system is to gather heat from the ground by means of ‘genuine’ geothermal energy. Therefore you need to drill holes into specific types of rock which are kept very warm by the decay of radioactive minerals. One of the few disadvantages of such a temperature control system is that it is dependent on the presence of hot bedrock. This is a rare condition and suitable geological conditions exist in only few locations. Until now this lack of suitable conditions effectively prevents widespread application of true geothermal sources. Normally, ground and groundwater temperatures are 50 to 55°F. These temperatures are too low to be used for direct heating. But with the modern groundwater heating technologies, it is possible to extract heat from such low-temperature energy sources and using it in combination with existing technologies. Groundwater heating is done by chilling the soil below. And conversely, the building can be cooled in summer as the heat pump works in reverse to shed heat into the ground.
Nowadays two kinds of groundwater heating systems are known to us: Open Loop systems and Closed Loop systems.
The difference between those two systems is that an Open Loop system pumps water, so it can draw water from a great distance. A Closed Loop system does not abstract water, but circulates fluid through a loop op pipes. A heat pump at the surface processes the water and extracts the energy to heat or cool. Afterwards the water is recirculated back into the ground. So a Closed Loop influences a relatively limited volume of ground. Of course it is important that with this limited influence the environment is not harmed, but the peak heating or cooling is limited as well. Most of the closed-loop systems have peak heating or cooling capacities of less than a few hundred kilowatts.
An Open Loop system actively pumps groundwater and therefore can use water from a great distance. So that results in a much larger capacity than a Closed Loop system, even up to 1 Mw! So Open Loop systems can be a serious option for larger developments, while the economic capacity of closed-loop systems is limited. But it also influences a much greater volume of ground.
In the the vision of Livin’ Green, Open Loop groundwater heating systems are not considered Renewable Energy systems, as they do require electrical energy for water pumps and heat pumps. Sources such as wind, water and solar do not require an external energy source and are therefore considered Renewable. But Open Loop groundwater heating systems are classed as LZC systems! That is because they are producing much more energy than the electrical energy they consume, up to three or four times more! And the best part is that if a system can be run via a simple heat exchanger to provide cooling, without using a heat pump, the ratio of cooling energy compared to electrical energy that is consumed can be 20 to 1.
While open-loop ground-source systems can offer great advantages in order to meet our future energy needs, nevertheless there are two key disadvantages.
The first one is the impact on groundwater resources. Dependent on the way the water is abstracted, such systems could seriously affect sensitive ecological sites like wetlands or delicate nature by lowering the groundwater level.
The second major disadvantage is the disposal of the water that has passed the system. Cooling will produce water that is warmer than when it started, and heating will produce a waste stream of cooler water. It is essential that we manage this stream of waste water if we want the implementation of ground-water source systems to be successful.
One way to manage is to re-injecting the waste water back into the soil or rock layers from where it came, via another set of boreholes. This possibility has the advantage it avoids surface water impacts and confronts us with sewer disposal. But this approach has a disadvantage too… If the extraction and re-injection wells are not separated wide enough, warmer or colder water may ultimately circulate between the extraction and injection and influence the optimal conditions
And the Conclusion?
Using groundwater as a LZC source of energy for heating and cooling buildings has real potential to reduce carbon emissions. It can save a significant amount of operational costs. Energy prices are increasingly rising and it is evident that they will not decrease again for a long time, perhaps never again… So that increases the economic advantages.
But future development and use of these systems has two major challenges:
1 The willingness of the government or other regulators to grant groundwater abstraction licenses for cooling or heating systems. Nearby abstractors and / or other stakeholders will have to be demonstrated that such systems will have minimal impact on their business.
2 The need to dispose lots of warmer or cooler water produced by the system. One option is to dispose of the waste water by re-inject it into the water holding layer. However, the risk is the migration of warmer/colder water between the abstraction and re-injection boreholes, affecting the long term efficiency of the system.
But nevertheless these kind systems can be a profitable way to heat or cool your house in the future, for both your purse and the environment. The impact on your energy bill will be huge, while the impact on the environment will be much and much less than the impact of using the traditional energy sources…
So it can be a very meaningful addition to the “Livin’ Green Lifestyle”…..
This article about groundwater heating is written by Victor.