Should new Swedish reactors produce heat besides electricity

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Should new Swedish reactors produce heat besides electricity

Postby Dag Lindgren » 17 May 2011, 11:30

I raise the question if Sweden could not use nuclear power more for heat production besides electricity.

Nuclear reactors produce electricity commercially, but very rarely heat. That means that two thirds of their energy production is spoilt on heating sea water. Nuclear power is able to increase its efficiency considerable by producing heat. In Sweden one of the first reactors heated a Stockholm suburb (Ågesta) and it basically worked. Some studies have been made later, but never led to anything. In Sweden with its long winters it might be of particular interest, compared to most parts of the globe, where winter is short and rather warm. A reactor optimized for producing water hot enough for a long transport and heating means it will produce somewhat less electricity.

Swedish electricity will increasingly be produced by windmills. Now windmills have an installed effect of 2200 MW, and this is rapidly rising. But the wind is seldom strong enough for full production and the wind may not blow when electricity is needed. The actual average output of windmills is around 22% of the maximum effect. Thus nuclear power is needed to assure a baseline production. Moments with surplus production of electricity will become more frequent, and when it could be useful if some of the nuclear power could be used for heat when electricity is not needed.

Swedish electricity production results in little carbon dioxide and other pollution, and does not strain limited resources, but heating does. Grids have been constructed for central heating with alternate heat sources, nuclear reactors could be hooked in on these grids. The technique for long hot water transports has improved. Heat as hot water can rather easily be stored for a part of a day to smooth out fluctuations, thus heat can be produced at reactors in nights, when the demand for electricity is low. The economy and efficiency of nuclear reactors could improve if they could help in heating. The economy of that combination could be favorable nowadays, even if it was not earlier. It is a large investment, but now when there is a long term decision making it probable that there is future of nuclear power it may be worth to do it.

There is a study initiated for reinvestigating the options to produce heat. But an input of ideas and comments at this stage may be useful.
Dag Lindgren
 
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Joined: 02 May 2011, 17:03
Location: Sweden

Re: Should new Swedish reactors produce heat besides electri

Postby Matte » 17 May 2011, 16:43

Terchnically we could, the infrastructure required is there. Problem is, we are not allwoed to as we can't increase the reliance on nuclear power.

Ringhals could supply the greater Gothenburgh area with heating, don't know what it would cost as you would need to rebuild the condensers or put heat pumps (freakishly large ones) in the seawater tunnels.

Ågesta, the first commercial reactor in Sweden did mainly supply heating to rural Stockholm, the electricity it produced was just an added bonus, as you correctly point out.

Windpower is a good way, if expensive, to save water in the hydroelectric dams. According to windstat the average output from windfarms is about 22% of installed capacity.

//Matte
Matte
 
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Re: Should new Swedish reactors produce heat besides electri

Postby Dag Lindgren » 18 May 2011, 18:03

The argument raised by Matte is (as I understand) that politicians did not allow Sweden to become more dependent on nuclear power. Yes, that is the major problem. Even if riksdagen recently (with a weak majority) has accepted that new reactors may be constructed, local hesitation is likely. The nuclear industry is confronted with the municipality politics instead of national politics and this interface may be less developed. Before it was even hardly allowed to make an outline of such a reactor, "tankeförbudslagen", and the prevailing idea was that nuclear was to be phased out within the foreseeable future. Certainly some will not feel enthusiastic for the vision of nuclear water running through their homes. The coming years we will live in the shadow of Fukushima. It is not politically correct with nuclear. Many do not view it as sustainable renewable. But on the other hand, the awareness of the urgency with global warming and climate gases are high. To use the excess heat from reactors may be a remedy. Some Nobel prize winners have recently suggested speading up this work, which motivates a new initiative which may be this. Waste of energy is not politically correct, and a general policy to save energy is less trustworthy, if nuclear energy is dealt with as a special case, where savings are less important.

There is also a question reliability of the system. Reactors may be out of service. A hot water system serves a smaller and geographically more constrained area than the electric grid. Other options are needed on a hot water grid. So it is today. Many different units produce hot water to the net. Some processes produce surplus hot water to the grid; use of some fuel solves a problem as destroing garbage; and some are designed to produce both heat and electricity with conventional fuel. Other production units produce only heat with fuel bought from the market and causing pollution, a large part of this fuel is fossil. It is the later type the nuclear hot water may reduce. But most of the production capacity is still needed as backup. Savings will be made on cost for fuel and reduction of pollution. The distribution safety and other factors mean that nuclear lines should not be designed to produce all hot water in the grid, but just a part of it. With a suitable design it may also be possible to use this reserve capacity at moments when it is a lack of electricity on the grid or a need to save available water in hydropower dams.

Matte mentions the option of heat pumps (freakishly large ones) in the seawater tunnels, but perhaps the electricity for heat pumps is more efficiently used for specific local projects instead of general solutions via long hot water transports, if this type of heat pumps considered. It may better to construct new reactors with production lines more directed to hot water. An idea may be to deliver 100 MW as hot water at a cost of reducing the electric output by 20 MW in a first effort to get the system implemented. The potential is much larger, but implementation and full scale test of the idea is easier with a limited project.

The rather small scale itself may be a risk. It is limited for as well the nuclear industry and the city, so why bother?
Last edited by Dag Lindgren on 18 May 2011, 20:45, edited 2 times in total.
Dag Lindgren
 
Posts: 13
Joined: 02 May 2011, 17:03
Location: Sweden

Re: Should new Swedish reactors produce heat besides electri

Postby Matte » 18 May 2011, 20:26

I will not comment on the politics as I like my blood pressure where it is, thank you.

However, putting heatpumps in the coolingwater tunnels would be the worst (but simplest option) to recover some of the waste heat from a nuclear power station.
Better yet would be to build a heat pump in the condensers. This would have 2 effects;
One you would increase the electricity output of the powerplant due to increase in Delta-T.
Two you get high quality heat to distribute to the districtheating grid.
Swedish reactors are usually off grid in the summer where the need for heating is low. The system would be sensitive to disruptions, but the incentive would be greater from the operator to maintain the plant(s) to keep the running. Swedish reactors can be run at an availability factor of >90% if the will to do so is firm.

I do agree that wasting all that energy is seriously silly...
Matte
 
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