FVB: Ulrika Ottosson, Heimo Zinko Lund University: Janusz ... konf...RHC 2012 / Next Generation District Heating / Lund University / 2012-04-26 Network operation and design Heat and

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

RHC 2012 / Next Generation District Heating / Lund University / 2012-04-26

Network operation and design

Heat and power production

Substation/HVAC design

Economy and environment

Next Generation DH in Sweden

Today: Large market penetration, almost 60 %

Future: Changed heat load profiles to expect

Impact on:


New Developments

Residential Changes

Retrofitting Existing Areas

Densifying City Center


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


0

10

20

30

40

50

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000 8500

DH

Lo

ad (

W/m

2)

Duration (h)

DH load before retrofit (W/m2)

DH Load with 20% reduction in space heating load (W/m2)

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)

How different measures changes the DH load


Yearly consumption various scenarios

0 kWh/m2

20 kWh/m2

40 kWh/m2

60 kWh/m2

80 kWh/m2

100 kWh/m2

120 kWh/m2

140 kWh/m2

160 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

District Heating Electricity


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


Yearly Load for Area of Single Houses (50 low energy houses, of which half have solar heating)

0

10

20

30

40

50

60

70

80

90

100

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

En

erg

y (

MW

h)

Heating (MWh) DHW (MWh)

Appliances (MWh) Secondary Connection Heat Losses (MWh)

Primary Connection Heat Losses (MWh)


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


• 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

Single detached house area – secondary

connection to DH system


Next Generation DH substation

• Forced air ventilation with heat

coil providing low return

temperature





temperature

• Domestic hot water prioritization

with or without directly

connection of waterborne

heating





temperature




heating

• Flat substations in multi-

residential building





temperature




heating

• Flat substations in multi-

residential 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, low-

temperature 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


– 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)

Literature review


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

[email protected]

• Patrick Lauenburg, Lund University

[email protected]

mailto:[email protected]

mailto:[email protected]

Documents

FVB: Ulrika Ottosson, Heimo Zinko Lund University: Janusz ... konf...RHC 2012 / Next Generation District Heating / Lund University / 2012-04-26 Network operation and design Heat and