COMBINED HEAT & POWER
Integration of all energy sources is the key
Around 40% of the energy requirements of UK buildings could be met from energy that is currently being lost. This could be from industrial processes, data- centre cooling (heat rejection), wastewater and numerous other sources. Sector coupling (an approach which integrates these multiple sources into district energy networks) has a crucial role to play in harnessing this potential. That’s the view of Paul Croft, business development manager – district energy, Armstrong Fluid Technology
T
he UK has set ambitious targets for district energy schemes as part of a national sustainability strategy, and the potential is huge. Currently around 3% of UK buildings are connected to district
energy networks, but the government (BEIS) has stated that, by 2050, the figure needs to 20%.
Sector coupling links energy streams and allows energy storage in various forms to match changing demands, as well as changing outputs, during a typical 24 hour period. Using this approach, energy supply is split into 4 key power grids: Electricity, Gas (a mix of natural, biogas, hydrogen etc.), District Cooling and District Heating. The four grids are divided into four areas where the energy is ‘obtained’, stored, converted, or used. The source and the use are straightforward, and diversity is a real advantage. The storage and conversion, however, facilitate flexibility and allow energy to flow across the four different power grids. End users can be consumers or prosumers, taking or giving energy into the system. So, you can think about sector coupling as a network in which energy travels in all directions across every connection. Energy of all types can move from, or to, the storage, conversion, and end use sectors.
A range of technologies, including biogas,
hydro-electric, nuclear, geothermal, wind, solar, and large scale CHP are brought together within an integrated district energy network. Some sources will be available 24 hours a day, every day, such as nuclear for example, whilst the availability of some sources could fluctuate wildly, for example solar or wind. Geothermal, solar and heat pumps could supply energy directly into the district heating network. If renewable energy is in abundance at a particular time, then this excess energy can be stored.
CHP offers obvious benefits in this context. The ability to locally generate electricity whilst also offering practical uses for the heat by- product is an appealing concept. The ability to utilise this excess power in the grid is what makes CHP so important in the sector coupling approach. Heat generated by the CHP plant can be combined with waste heat from industrial processes, wastewater treatment plants, hospitals or even data centres. The heat is then captured, allowing the opportunity for it to be stored and utilised within the district energy network to provide heating, hot water
or even cooling for other buildings in the network. Demands can be met for a number of different types of building, whether their purpose is industrial, commercial or residential. As a wider part of the energy security debate, as well as the cost of living situation, it’s vital that investment into the country’s infrastructure is as well spent as possible. Sector coupling can play a vital part in easing fuel poverty and reducing carbon impact, while giving local authorities and government department vital levels of control in an unpredictable energy market. So how exactly can CHP be effectively integrated into district energy networks using the sector coupling approach?
CHP’s role in sector coupling
CHP is an extremely useful tool in a district system, offering two different energy outputs and therefore adding greater flexibility to the energy grid to meet peaks in demand. It also provides the additional security of energy supply at times when wind or solar, for example, may not be available. Large scale CHP, located
strategically, fits well into a ‘smart grid’, particularly in locations where the nature of the existing housing or building stock requires higher temperatures from the district network than would normally be required. The electricity produced by the CHP can also be used to power large scale heat pumps or electric boilers to further increase the thermal input into the local buildings (loads permitting). Locating CHPs as close as possible to where they are needed reduces the losses associated with electricity transmission, as well as the thermal losses of LTHW transport.
Thermal store essentials
The thermal store isn’t just a simple store of energy, it functions as a window on the relationship between energy output (or availability) and energy demand on the network. The thermal store is a ‘reservoir’ of energy ready for periods of high demand. It allows low carbon sources to carry on running even when demand is low, maximising the utilisation of the low carbon source as they refill the thermal store and create greater flexibility and reliability of the system. Within a district heating network, the peak demand period is short and, for the majority of the time, the load will be less than half of the calculated peak.
This can allow, with careful sizing of the
thermal store, for the total capacity of the energy sources to be lower than the calculated peak energy demand. The thermal store is utilised during peak demand times and can be replenished by the energy sources during times of lower demand.
Smaller heat networks and communal systems
On smaller systems where thermal storage capacity is limited, it’s important to maximise the energy contained in each capacity. On this type of application, small modulating CHP units are ideal. The thermal store allows the CHP to operate for a longer period, even when the thermal demand has dropped below the minimum output of the CHP. This allows the CHP to continue providing electricity, either into the building or back to the grid.
30 BUILDING SERVICES & ENVIRONMENTAL ENGINEER APRIL 2025 Read the latest at:
www.bsee.co.uk
H S IA
OPT L
C MI E
O BND HA O E E T P WR
RNW BE I D S R
E E A L N UT Y
GO HR A
E T E M L
BO AS I M S
I E S O A E C T R G
F E O LN
R E C OI G
E E GNR Y F O R M W S EAT SA I N
P WRO E T TO
O G NC R A I R N I E C CE A KN Y L
HA U P E T P M
S L R F R
OA A M
DT E TR AA CNE
HMSO E WT
IH S L ROA
E EGNRY SOA E T R G
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42
