Next Generation District Heating FVB: Ulrika Ottosson, Heimo Zinko Lund University: Janusz Wollerstrand, Patrick Lauenburg, Marek Brand (DTU) a project The Swedish District Heating Association s R&D programme
Next Generation DH in Sweden Today: Large market penetration, almost 60 % Future: Changed heat load profiles to expect Impact on: Network operation and design Heat and power production Substation/HVAC design Economy and environment
Residential Changes Retrofitting Existing Areas Densifying City Center New Developments
Increased energy efficiency in area Rud, Karlstad ( million programme building) Improved building envelope Exhaust air recovery Improved control Reduced annual heat load and peak load
DH Load (W/m2) How different measures changes the DH load 50 DH load before retrofit (W/m2) DH Load with 20% reduction in space heating load (W/m2) 40 DH Load with 20% reduction in space heating + Heat recovery ventilators (W/m2) DH Load with 20% reduction in space heating + Exhaust air heat pumps for rad (W/m2) DH Load with 20% reduction in space heating load + Exhaust air heat pumps for rad and DHW (W/m2) 30 20 10 0 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000 8500 Duration (h)
Yearly consumption various scenarios 160 kwh/m2 140 kwh/m2 District Heating Electricity 120 kwh/m2 100 kwh/m2 80 kwh/m2 60 kwh/m2 40 kwh/m2 20 kwh/m2 0 kwh/m2 Before retrofit 20% Space heating reduction 20% Space Heating Reduction + Heat Recovery Ventilators 20% Space heating reduction + Exhaust Air Heat Pumps for rad 20% Space heating reduction + Exhaust Air Heat Pumps for rad&dhw
New Development with Single Detached Houses A low heat density area with 58 dwellings (50 connected to DH) low energy houses and houses with solar collectors Connection to main DH network
Energy (MWh) Yearly Load for Area of Single Houses (50 low energy houses, of which half have solar heating) 100 Heating (MWh) Appliances (MWh) Primary Connection Heat Losses (MWh) DHW (MWh) Secondary Connection Heat Losses (MWh) 90 80 70 60 50 40 30 20 10 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Single detached house area primary connection to DH system Pressure either increase pressure in whole system or booster pump Same temperatures as the whole system, i.e. substantial heat losses Pipes, components and substation must be designed for high pressures and temperatures higher installation costs and limited freedom for system layout
Single detached house area secondary connection to DH system Pressure 1-1,5 bars at area substation enough For new-built houses supply temperature of 60-65 C enough Plastic pipes can be used which can reduce installation costs May result in multiple heat exchange
Next Generation DH substation Forced air ventilation with heat coil providing low return temperature
Next Generation DH substation Forced air ventilation with heat coil providing low return temperature Domestic hot water prioritization with or without directly connection of waterborne heating
Next Generation DH substation Forced air ventilation with heat coil providing low return temperature Domestic hot water prioritization with or without directly connection of waterborne heating Flat substations in multiresidential building
Next Generation DH substation Forced air ventilation with heat coil providing low return temperature Domestic hot water prioritization with or without directly connection of waterborne heating Flat substations in multiresidential buildings In case of solar heating for domestic use domestic hot water storage
Consumer installations Not evident what HVAC system will dominate in the future Radiators, underfloor heating, airborne heating New control systems required Not only outdoor temperature important, but much larger influence from human behaviour Heat supply via air in the first Swedish passive houses, but indications for comeback of waterborne heating
Literature review Experiences from e.g. Denmark, flat substations, lowtemperature DH Low energy buildings Evaluation of passive houses In general good, but bathrooms generally in need of heat source Comfort heating often requested by users Heat supply when ventilation is turned off (during vacations etc.) Concerns regarding heat distribution via air
Literature review Indoor temperature in low energy buildings mainly affected by variations in internal heat gains not outdoor temperature Fast variations, but long time constants due to good insulation Different opinions regarding use of underfloor heating (and comfort floor heating)
Literature review Passiv houses industry has not disqualified waterborne heating, only a matter of economy A positive attitude towards DH as heat source in future low-energy houses (Not an equally positive attitude towards DH industry)
Adaptive control of radiator systems - a way to reduce supply temperatures? Continuation of a successful project were a new control algorithm for radiator system control was developed By control of not only radiator supply temperature but also radiator system flow rate, the return temperature could be reduced by approx. 2 dgc in four tested buildnings The algorithm will adapt to external changes, e.g. an improved building envelope or a reduced DH supply temperature. Simulations show that can be a useful tool to handle existing buildings in an area where you want to reduce the network supply temperature
Other studies within the project Field study of old secondary network Two equal secondary systems, both with 80 detached house built during 70ies, one of these performs poorly Methods to optimize temperatures and flow rate Comparison of different heating systems radiators, underfloor heating and forced air heating with regards to return temperature, peak load and operating hours
Thanks! Ulrika Ottosson, FVB ulrika.ottosson@fvb.se Patrick Lauenburg, Lund University patrick.lauenburg@energy.lth.se