By George Harvey
One of Scotland’s greatest cities, Glasgow, sits on the banks of the River Clyde. Its situation on that river is a resource that Star Renewable Energy (SRE) is taking advantage of to provide district heating.
SRE is an offshoot of Star Refrigeration, which was founded in 1970 and is one of the largest industrial refrigeration engineering companies in the United Kingdom. The company started producing heat pumps to capitalize on a number of technological advantages. .
General technologies for heat pumps are not new, but it was necessary to get away from the use of chlorofluorocarbons, which produced the hole in the ozone layer, and chlorofluorocarbons, which are greenhouse gases, and the engineers at SRE knew they could do this with ammonia. With half of northern Europe’s fossil fuels used for heating, heat pumps had great potential importance. Efficiencies of scale made district heating increasingly important. Heating with fossil fuels is expensive and contributes to climate change. All of these made large heat pumps a good option to consider.
SRE solved all these problems by working on the idea of doing district heating with a river-sourced heat pump. The system using ammonia is much kinder to the environment than the synthetic carbon compounds usually used for refrigeration. The result was a system that does not need to release any greenhouse gases at all, if the electricity that drives it is entirely carbon-free. It is also considerably less expensive to run than using natural gas.
For those who do not understand heat pumps, nearly all of us already live with at least one. Heat pumps power the refrigeration and air conditioning in most homes. The heat pump in a refrigerator extracts what heat it can get from inside the refrigerator, and discharges it into the kitchen.
In the American northeast, we have seen a strong movement toward air-sourced heat pumps, which are among the best choices for saving money in heating. More efficient, but often much more expensive initially, are ground-sourced heat pumps. A good choice for those who have a good body of water nearby is a water-sourced heat pump, which has most of the advantages of both; its special problem is that if the water is in a pond, it must be large enough or it can freeze. The river-sourced heat pump may provide a best case for heating, because when the water gives up its heat, it just flows on, and new water provides its heat to the pump.
SRE is using river-sourced heat pumps for district heating, so a number of buildings can benefit from the efficiency a large unit can provide. This may be the least expensive heating most of us would encounter, outside of a Passive House.
The heat pump SRE is providing in Glasgow will cost £3.5 million. The fluid it uses to deliver heat to nearby buildings will be heated to 80° Celsius (176° Fahrenheit). Carbon emissions are reduced by at least half, and possibly to zero. There are no oxides of nitrogen emitted, and there are no particulates. The result is a system that is kinder to the environment, safer for the health of the people, and nonthreatening to the climate.
One of the interesting things about this is that most cities are built on rivers or large bodies of circulating water, such as the sea or the Great Lakes. This means that the special advantage Glasgow gets from its first river-sourced heat pump could be realized by many cities in exactly the same way. New York City could be heated by water not only in the Hudson River, but in Long Island Sound and New York Harbor.
There are limitations to the amount of heat we can reasonably extract from rivers. It would make good sense to bear these in mind as we move forward. Nevertheless, the large heat pumps built by SRE look like they may represent an important heating solution.