Nuclear plants operate at only a few hundred degrees Celsius, so they don’t have very high thermal efficiencies. Thus only a small part of the nuclear energy is changed into electricity and most is lost with the coolant fluid, about two thirds. Could it be used for something?
Traditional coal plants have long given their waste heat for district heating (and some cooling in the summer too!). This “free” energy is distributed as hot high pressure water in large pipes. It works great, especially in dense areas. This reduces coal usage quite a bit if you compare it to heating with coal electricity, or oil usage if you compare it with heating with heating oil.
In Russia special nuclear power plants, especially for isolated cities included provisions for large amounts of district heating. Though this means that the plant needs to be quite close to the city for it to be effective. It’s not done in the west. Could it work in Finland?
The power company Fortum is probably building a third unit to the Loviisa power plant complex some 100 km east of Helsinki, and it’s proposing to Helsinki that the new unit could provide a gigawatt of cheap district heating for the city. But Helsinki at the moment owns its own power generation company, Helsingin Energia (Helen), and is sceptical of the idea. Helen’s coal plants provide the current district heating and there are rules about the maximum size of a plant in the grid – if over 40% of the district heat would be provided by one plant, when it went down for some reason., there could be a catastrophe.
A 100 km long very large hot water tube system might also be very expensive. There exists a roughly 100 km long fresh water tunnel carved in rock, providing water to Helsinki from lake Päijänne, so there is some expertise regarding such large scale subterranean building.
Another way of thinking about nuclear heating is to generate normal electricity but use it to power a heat pump at the heating location. This can increase the heating power as much as five fold – ie 5 kW of heating for 1 kW of electricity. This requires no district heating pipe infrastructure but the heat pumps are expensive. They are becoming more common in less dense living areas though and are a good way to reduce electricity use if they replace direct electric heating. They also increase peaks since the five multiplier can drop to two when it gets much colder outside – because the temperature difference that the pump works against is larger.
Helen is a very good business for the city and its profits lower the local tax rate quite a lot. Those fools in the neighbouring city of Espoo sold their own power company abroad, started playing in the stock market with the money and have lost quite a bit. (And that was before the recession!)
Helen is also a stakeholder in the Olkiluoto 3 nuclear plant that is being built in Eura, in Western Finland, they’ll use part of the electricity that will be generated there. The consortium leader, Teollisuuden Voima, is a competitor to Fortum.
There seems to be no love lost between Helen and Fortum.
Nuclear power plants have been proposed for city part heating, one was even in operation in Sweden. It was built securely inside rock, but it was shut down after a mishap. There were plans to put such a small nuclear plant in the Malmi northern suburb of Helsinki in the sixties or so, but that plan was cancelled. Also, in the past, the large Granö island in front of Helsinki’s east side neighbour Sipoo was charted for a nuclear power plant, but it was cancelled and in the end only Loviisa and Olkiluoto were built. Now that the western part of Sipoo has been grabbed by Helsinki, some have proposed to dust off the old plans and put a reactor on the island. 🙂 At one point when no plants had been built yet in the country, Inkoo, some 50 km west of Helsinki was also one of the possible plant locations. The pipes from there would have been easier. There already exist quite large power grid connections in Inkoo because an emergency coal plant is located there. It could be one compromise site for a small nuclear plant – far enough but not too far.Sources: personal communications with various people, an article in Tekniikka and Talous (in Finnish) and Finnish Wikipedia on Finnish nuclear history and air heat pumps.