District heat networks that use locally available waste heat could be key to delivering on the UK’s low carbon energy commitments. Will Stirling reports
Engineers in the energy distribution and heating industry are working on a daunting but exciting challenge that recently received a government boost.
About half of all energy consumed is used to generate heat and hot water and, to achieve government carbon targets to comply with UK’s Paris Agreement obligations, the carbon intensity of this energy needs to be reduced by 90 per cent by 2050. As vast amounts of waste heat produced by sources from processing plants, data centres and even sewage are going, literally, up the chimney, it’s little surprise that the UK’s energy and heat policy is now focused on capturing this heat to distribute it to consumers, cutting CO2 emissions and lowering the amount of energy required to heat water.
Engineers and heat experts are looking to Europe to adopt a system that redesigns heating and energy into a smart, decarbonised, integrated system – heat networks.
Traditional heating systems like gas boilers, tend to be binary – either “fully on” or “off”, requiring high energy inputs to raise the temperature of water from the ambient temperature to be useful for heating buildings, say to 40°C. A heat network, drawing heat from waste sources, is designed to supply water at a higher temperature than the environmental temperature (that might be 10°C or lower), thereby lowering the energy needed to heat it up.
Other appealing features of a heat network is that a well-designed system can be used for both heating and cooling. It also sources what is locally available, minimising the expensive transportation of heat as well as using untapped sources such as a processing plant, data centre or ground source.
“Britain has been very good at decarbonising electricity but decarbonising heat on a mass scale has been left in the too-difficult-to-handle box,” said Dr Eoghan Maguire, head of business development at Vattenfall Heat UK. “But it is now addressing heating, and is starting to address transport, and connecting the system better through sector coupling.”
Vattenfall Heat has 2.2 million customers in Europe. It is helping to transform Amsterdam’s heat and energy demand into a smart grid involving recharging points for electric vehicles. It is now bringing its heat network expertise to Britain, establishing Vattenfall Heat UK in March.
Now the government has come on board. In October 2018, the Department for Business, Energy and Industrial Strategy (BEIS) launched the latest stage of a £320m programme to encourage the mass rollout of heat networks. Heat network developers are being offered grants of £5m and loans of up to £10m as part of the Heat Network Investment Project, or HNIP. The government is hoping to unlock around £1bn of investment using the seed funding.
When HNIP was first launched in October 2016, the government stated that the full programme would aim to draw in £2bn of public and private sector investment. A BEIS spokesperson said it will assess first round applications in spring 2019. The first funding awards are anticipated in the early 19/20 financial year.
Urbanisation is the driver
For engineers, the scale of the task of meeting carbon reduction targets by 2050 appears more achievable when the potential for district heat networks in Britain is taken into consideration. The example of some European countries, especially Germany and the Nordics is notable. In Berlin for example, 30 per cent of the city’s demand for hot water and heating is met by the district heat network that is owned and operated by Vattenfall, with suppliers including E.ON providing even more of the city’s heat network. That proportion is constantly growing in line with the network’s expansion, currently running at the equivalent of 22,500 households per annum for Vattenfall alone.
“We believe heat networks have a huge part to play in contributing to carbon reduction both in the UK and globally – currently supplying around 2 per cent of UK heating demand but with the potential to supply up to 18 per cent by 2050,” said John Armstrong, head of operations, UK District Heating at E.ON, which also has a big footprint in Europe and operates more than 60 district heat networks in the UK, including the Cranbrook district heat network (DHN) in Devon, which is geographically its largest and is expected to lower CO2 emissions by 13,000 tonnes per year once all of its properties are finished and occupied.
While Cranbrook is a town using a ‘community energy centre’ as the heat source, big cities are at the heart of the heat network proposition. As populations in big urban environments expand, this puts pressure on heating infrastructure and carbon emissions. “In particular, heat networks are essential to providing energy in cities, which consume two-thirds of the worlds energy and contribute 70 per cent of the world’s CO2 emissions,” said Armstrong. “By 2050, 66 per cent of the world’s population are expected to live in cities by 2050, an additional 2.5 billion urban residents, so we see heat networks as a major part of the solution.”
Vattenfall’s Eoghan Maguire said studies show that the overall demand for heat in London is 66 TWh (terawatt hours) per year. “A recent study done for the Greater London Authority shows that the total heat delivered from secondary sources in London was 71 TWh,” he said, showing that super-efficient heat capture could theoretically make heating London virtually fossil fuel resource neutral. “We are currently wasting heat that is going up the chimney and is literally producing global warming. This cannot continue.”
The engineering design
An important feature of a heat network is that it uses its environment in the best way to capture and distribute heat. Heat networks are designed in two principal ways. One is a centralised system with a large single source of heat coupled to a heat pump, more of a giant heat exchanger, that adjusts the temperature of the original heat to a useful level, and the decentralised system that uses multiple smaller boilers in buildings, an integrated network of mini units.
“Where we see there is a large readily available waste heat source, it is viable to adjust the temperature and transport this heat in pipes, but you don’t want to transport it too far away to remain an efficient system,” said lead engineer at Vattenfall Heat UK, Sandra Slihte. “Where there is no readily available waste heat source, the conduit is copper wire [rather than pipes] in a network of local heat pumps in buildings to create a system. There will be a combination of both these systems in the UK on a case-by-base basis.”
One feature of heat networks being pursued by the utilities in the UK is a low temperature network. Such networks allow you to use lower grade heat – for example, the heat rejected from refrigeration or air conditioning. E.ON has experience of operating heat networks in both Europe and in the UK and is looking to develop the technology through next-generation low temperature networks such as E.ON’s “Ectogrid”, which delivers higher efficiency through decentralising energy generation, enabling buildings to both push and pull energy into and out of the network. “If you use a lower temperature network you can then use that heat again so you can almost recycle the heating and reuse it several times as it passes through the urban environment,” said John Armstrong.
And the rise of heat networks should be good news for manufacturers. Today much of the physical infrastructure for energy centres and connecting plants to the network are imported from big DHN markets like Germany. More DHNs in Britain will create a bigger market for pipes, valves, pumps, heat exchange kit and control systems.
Applications for the main £320m HNIP programme opened on 4 February. A BEIS spokesperson said: “The Heat Networks Investment Project has created a route to market for innovative energy projects across the country and demonstrates a key objective of the Clean Growth Strategy: to deliver technologies that lower bills, cut carbon and improve the quality of life for communities across the country”
Great news, decarbonising heat is needed urgently. It’s a superb challenge for engineers and non-engineers to come up with the most effective and most creative solutions.
Here is one such solution:
“Energy saver number one
Kungsbrohuset in Stockholm is a building heated by people. A number of unconventional methods help to minimize energy consumption in the Kungsbrohuset Building in Stockholm. Like recovering excess body heat produced by the some 200 000 commuters that pass by the Central Station every day. Or that the building’s windows let the daylight in, but blocks out the summer heat.”
http://www.symbiocity.se/en/approach/Cases-undersidor/Kungsbrohuset-people-power/index.html
When I was regularly going to Poland about 20 years ago, they had this. Domestic rubbish etc fed the boilers and the steam or hot water was distributed in large pipes, possibly 40cm diameter. The drawback was that the lagged pipes running alongside the roads and taken over entries on bridges were unsightly. However, the pipes avoided damage from heavy trucks crossing their path, if underground. The recipients of the heating were grey, monolithic Soviet style blocks of flats but it did mean that there was a lowered fire risk and all the inconvenience of fireplaces and fuel in high-rise flats was avoided. I just hope the government takes into account the aesthetics!
If I’m reading this correctly the heat pump is at the wrong end.
Steam is an efficient way of getting a lot of heat down a small pipe, so if you burn fossil just for heating, steam is a good option, but that’s not CHP.
Traditional CHP takes heat out of the heat engine hotter than normal, to be at a useful temperature, but that massively reduces the efficiency of the power station (increasing carbon emissions). If you are using waste heat, you want to send it round the network at whatever temperature the free heat is available. The disadvantage is that by the time you put it through a passive heat exchanger inside a remote building, it might not be hot enough to heat effectively.
So you need a heat pump somewhere. If you put the heat pump at the remote end, in place of a passive heat exchanger, suddenly the whole thing becomes viable.
You don’t have to reduce the efficiency of the PowerStation and the heat losses in transmission are less (also you haven’t actually paid for the heat you lose in the network).
(The underground problem is unique. I has taken 150 years to get too hot, so it doesn’t require continuous cooling. Pumping the heat out, in winter, when the waste head would be useful is sufficient. (It won’t warm up much in the six warmer months of the year).))
Laudable, but very difficult to make this cost-effective as retrofits I would think? Better to ensure that developers incorporate such ideas into new build warehouses, offices, housing estates etc?
This is not a completely new idea, rather it is a new way to apply the physics/chemistry of what he have in hand. Taking a diffuse 40 degree heat, then upgrading this to a lesser amount of heat at a higher temperature can take place with small electric power input. Taking a low temperature source that already contains some fuel value, then burning that appropriately (H2 and CO by air) will result in more heat, but also now at a higher temperature, allowing an additional layer of generation (fuel cell with some waste heat perhaps), and the carbon output is minimal, depending upon the ratio of CO to H2 in this hypothetical fuel source.
Some interesting comments.
I am not convinced of the decarbonising nature of the companies involved – as they talk of CHP (with gas, biogas, oil, electric [?]) – but not sure these are free of net carbon dioxide contributions. And they all seem focussed on big city projects.
What interests me is the heat storage and heat transmission – both are subject to losses if poorly engineered; and it seems that using higher temperature differences would reduce the size of pipes (say to 4cm) required (eg liquid nitrogen for “coolth” as compared to chilled water) – and possibly high temperature liquids as opposed to steam. [Such a reduction would make pipes easier to install or post-fit – as well as providing a premium energy, and likely safer than high temperature steam. Perhaps another transmission analogy would be 12 volt power transmission as opposed to an 11kV line…].
It sounds somewhat like a new renewable heating initiative – but writ for large companies and focussing delivering old fashioned technologies.
There have been many attempts to justify district heating over the years. A number of dedicated and local schemes have been installed very successfully (Nottingham and Sheffield), and a lot of industrial CHP schemes have developed.
However, as all of the serious studies have found, the capital investment to alter cities or towns to use district heating are prohibitive. New towns have a better potential case. The crux of the problem lies in the fact that winter heat demands are about 7 x power demands and the investment is only properly utilised for 4 months of the year. Additionally, the low summer heat load is a major problem for district heating schemes as they must continue to work even though the demand is negligibly small.
The case for scrapping our efficient gas fired central heating systems is totally dependent upon the belief that somehow the UK’s self-harm can benefit the world and have a measurable impact on CO2.
Electric heating would be ideal. No need for plumbing and pipework around the building. Easy to install. No heat losses from pipework. No inefficiencies from boiler combustion process.
Its up to the government to bring down the cost of electricity to match the gas rates.
Good point. But cheap AND reliable power generation (when needed) – just like (rail) travel – seems to be too complex an idea for politicians and civil service (perhaps it requires understanding of economics not covered in the PPE lectures?)
Some interesting comments.
I am not convinced of the decarbonising nature of the companies involved – as they talk of CHP (with gas, biomass, oil, electric [?]) – but not sure these are free of net carbon dioxide contributions. And they all seem focussed on big city projects.
What interests me is the heat storage and heat transmission – both are subject to losses if poorly engineered; and it seems that using higher temperature differences would reduce the size of pipes (say to 4cm) required (eg liquid nitrogen for “coolth” as compared to chilled water) – and possibly high temperature liquids as opposed to steam. [Such a reduction would make pipes easier to install or post-fit – as well as providing a premium energy, and likely safer than high temperature steam. Perhaps another transmission analogy would be 12 volt power transmission as opposed to an 11kV line…].
It sounds somewhat like a new renewable heating initiative – but writ for large companies and focussing delivering old fashioned technologies (eg a network would, in fact, be a local monopoly…)
Vienna was refitted with DH recently for a total cost of around 6000 Euros / building connection.
Creating DH public utilities ie statutory DHC legislation is key to unlocking low cost and low risk finance as is used in the public utility companies eg gas, electricity. In Denmark many of the District heating schemes are owned by a user cooperative or local municipal authority, quite often better value than a profit orientated company.
DH is not limited to just cities but villages with reasonable densities often have small DH schemes.
DH can not only use waste heat but also solar thermal energy , a free fuel , as is being done in sunny Denmark, a cloudy climate similar to the UKs, with many schemes installed using low cost, large scale, insulated inter-seasonal ponds (or boreholes), see solarheatdata.eu/
The temperature of the heat source and the heat loss of the buildings according to the laws of thermodynamics should dictate tempertature distribtion, ie high temperature combustion source CHP should be distributed at high temperatures and matches the heat demand of legacy buildings in city centres. You can have then cascading lower temperature networks using the hot return and lower temperature renewable / waste sources….
If UKs appalling new build thermal performance standards and paltry thermal renovation standards were improved then low temperature renewable district heating (4DH – 4th generation ~ 60-35C) could be used widely.
In UKs moderate climate mostly it is cheap and poorly designed buildings that require cooling, viz UKs appalling thermal performance standards.
In Denmark many of the District Heating (DH) schemes are owned by a user cooperative or local municipal authority, quite often better value than a profit orientated company. As they are public utilities they have access to low cost and low risk finance. UK should implement statutory public utility DHC legislation to unlock this finance.
DH is not limited to just cities but villages with reasonable densities often have small DH schemes.
The temperature of the heat source and the heat loss of the buildings should dictate temperature distribution, ie. high temperature combustion source CHP should be distributed at high temperatures which matches the heat demand of legacy buildings in city centres.
Cascading lower temperature returns can be used with lower temperature waste heat sources and renewables to feed lower heat density suburbs particularly with improved building thermal performance standards (lower heat densities) at lower temperatures eg. 60-35C supply/return 4th generation DH. Renewable solar thermal using large, low cost pond (or borehole)
at €25-30/m3 are increasingly being used in sunny Denmark (similar cloudy maritime climate to the UK), see http://www.solarheatdata.eu .
Also with a large national renewable energy system excess renewables can be dumped in DH, a lower cost than batteries and overly expensive slow to build nuclear, to meet the large heat demand of nearly half of all energy demand in the UK eg. wind via the HV network can use MW sized heat pumps (water sourced) to upgrade large scale inter-seasonal solar to DH distribution temperatures, see planenergi.eu/activities/district-heating/seasonal-heat-storage/
UKs appalling new build thermal performance standards and paltry thermal renovation standards need urgent upgrading to make the most of DH. As do DH design standards particularly architects who do not design frequent service risers to minimise primary laterals!!
In UK’s moderate climate mostly it is cheap and poorly designed buildings that require cooling, viz UK appalling building thermal performance standards.
And it does not necessarily cost more if well designed eg Wolverhamton passivhaus energy standard schools same budget as standard Building Reg buildings, see http://www.youtube.com/watch?v=MffKNX5qlLw&playnext=1&list=PLAD94D448BBA00BB9&feature=results_main
Excellent pieces, John. I was in Vienna last year and saw no sign of the DH network being built. I thought that it already had DH?
The big problem traditionally was the justification of the capital cost of DH given its low utilisation factor. However, as you note, it has had a number of specific successes where well planned developments occurred. The Nottingham scheme is old but first class, for example, probably its biggest problem is supplying the low summer demand using a common network. It uses staged let-down , which was right when the heat came from coal or waste fired boilers.
The fundamental problem is with the theory behind heat engines. We are still using the Rankine cycle theory behind every heat engines and gas turbines for around 200 years. This theory says at least 50% heat should be lost to sink . But we need a theory which should be a least 85% efficient to design heat engine and gas turbine same like electric systems with more than 80% efficiency. The theory is already there in nature. But no one wants to promote it.