Project scenario heating costs
Assuming the respondents in the survey are representative of the local population, and based on an 85 % subscription rate to the plant, total estimated heating demand from the plant is:
- 0.85 * total heat demand for the area
Total Heat Demand for the Area
In Reference Scenario Heating Costs we calculated heating based on litres of oil consumed, equal to 5 526 MWh/year. Actual heating demand is a fraction of this, as there is some loss from the furnace to efficient heating demand. Assuming a furnace has an efficiency rate of 0.84 (a middle value based on new and slightly older models, see Heat source efficiency);
- 0.84 * 5 526 = 4 642 MWh total heat demand from oil
It is normally assumed that electricity used for heat has no loss once it has reached the household, so the electricity consumption from Reference Scenario Heating Costs still applies.
- Total electricity consumption for heating: 530.4 MWh per year
For simplicity in this example, we will assume that all those who own oil-based boilers switch to the district heating plant, and the remaining 15 % use electricity for heating.
This results in a demand for heat energy from the district heating plant equal to:
- 4 642 MWh (oil) + 76.4 MWh (electricity for oil-based boilers) = 4 718.4 MWh
The remaining demand (outside of the district heating plant) is assumed met by electrical heating, and is equal to:
- 454 MWh/year
Total fuel costs for the area
The heating demand does not correspond to the heating consumption, due to distribution net loss and boiler efficiency rates of below 100 %.
Assuming a boiler efficiency rate of 0.84 (same as for the private oil burner above) and a distribution net loss of 31.5 %, total heating consumption becomes (approximately):
- (4 718.4 + ( 4 718.4*0.315 )) + ( 6 204.7*0.16)
- 4 718.4 + 1 486.3 + 992.8 = 7 197.5 MWh
Straw has a given combustion value of 14.5 GJ/ton (app. 4 MWh/ton), when it has a moisture content of 15 %. Oil has a combustion value of 0.036 GJ/liter (app. 0.01 MWh/liter).
Assuming the plant runs on 99 % energy derived from straw and 1 % energy derived from heating oil (at peak load), we have the following energy requirements:
- (0.99 * 7 197.5) / 4 = 1 781.4 tons of straw
- (0.01 * 7 197.5) / 0.01 = 7 197.5 litres of oil
Additionally, it is assumed that the district heating plant uses electricity equal to 13.4 kWh/MWh (average taken from the 2009 statistics on fjernvarme.dk, the Danish district heating website, based on reported values from straw-based district heating plants producing less than 20 GWh/year):
- 0.0134*7 197.5 = 96.4 MWh of electricity.
Based on figures from the DEA for 2004, fuel prices of oil are 74.4 DKK/GJ and fuel prices of straw are 31.4 DKK/GJ, excluding VAT and other taxes.
This gives the following fuel costs for household heating:
- 14.5*1 781.4*31.4 = 811 071 DKK for straw
- 0.036*7 197.5*74.4 = 19 278 DKK for oil
Electricity prices are 63.2 DKK/GJ and 550.4 MWh correspond to app. 1 981 GJ. For total electricity consumption for heating used in the area, total electricity costs are:
- 63.2 * 1 981 = 125 199 DKK/year
Total fuel costs for the area equal 955 548 DKK in 2004
Greenhouse gas emissions for project scenario
Consumption of heating oil of 1 GJ emits 74 Kgs of CO2. For electrical heating generated from central power plants, consumption of 1 GJ emits 236 Kgs of CO2. (Note that prior to 2008, the DEA did not estimate CO2 emissions for electricity ab household, as the price of CO2 is included in the household cost of electricity. The value used in this example is the estimate from 2008.) Straw heating emits 0 Kgs of CO2, as it is a CO2-neutral fuel.
- For an oil consumption of 7 197.5 liters, CO2 emissions equal 19.2 tons
- For an electricity consumption of 550.4 MWh/1 981 GJ, emissions are 467.5 tons of CO2
- Total emissions of CO2 in the project scenario are 486.7 tons
Cost of emissions
For simplicity, a CO2 tax of 90 DKK is assumed for the entire period in this example. This tax has to be multiplied by the net social impact factor of 1.17, resulting in a net cost of 105.3 DKK/ton of CO2.
- Total costs of CO2 can be calculated as 51 250 DKK for 2004