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Biomass case study

Replacement of an existing heating factory by a wood chipor pellet plant

1 Description of the case

A factory has to replace its old heating plant. Considerations regarding using biomass asalternative for oil have to be made. The present buildings include:

Description Aream

Heat transfer Heatingsource

Office 67,50 Hot water Oil boiler Other rooms 257,00 Hot water Oil boiler Work shop 1 423,00 Hot air Oil fired air

heaterWork shop 2 128,35 Hot air Oil fired air

heaterProduction hall 446,00 Hot water Oil boiler

Potential newproduction hall

( 5.350,00 ) Hot water Oil boiler

Sum 1.321,85( 6.671,85 )

Installed power:

Oil boiler: 104 kWOil air heater: 230 kW NennleistungHot water preparation: 2 small electric heaters

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2 Assessment of energy demand

The assessment of energy demand and heat load shows that in this specific case economic

measures for energy savings can be implemented, which decrease the heating load to 140kW. Such an assessment of energy saving measures is of particular importance, whenimplementing biomass heating systems. A later decrease of heating load can lead tooperational problems in case of overdimensioned biomass boilers. Renewable energy shouldalso be used as efficiently as possible.

The assessment of energy demand after realization of conservation measures has resultedin the following figures:

Description Heat loadkW

Final annual energy demandkWh/a

Office 11 14300

Other rooms 23 29900Workshop 1 51 66300Workshop 2 18 23400Production hall 41 53300Potential new productionhall

500650000

Sum without new productionhallSum with new productionhall

144

644

187.200

837.200

The calculated energy demand corresponds to 1300 hours of full load operation.

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3 Investment costs

Both boiler and oil fired air heater need to be replaced. The chimney has to be improved.It is considered to build a completely new large production hall due to a potential large newcustomer. New personnel will also result in an increased demand for hot water. Total heatload would increase to 650 kW.

Costs including installation and putting into operation (Note: These costs are real costs thathave been collected in Austria for 2004).

Device Investment costs (Euro)Oil boiler 150 kW 12.850Oil boiler 650 kW 33.000

Oil storage (for 650 kW): 10.000l 6.500Biomass boiler for dry woodchips, pellets (under feed stoker)150 kW

29.300

Compact boiler for pellets150 kW

24.000

Biomass boiler for dry woodchips, pellets (under feed stoker)650 kW

54.657

Biomass boiler for wet wood chips(moving grate)650 kW

60.380

Chimney improvement(for 150 kW)Chimney improvement(for 650 kW)

3.7459.072

Heat storage tank 0,6 / Liter Wood chip storage (concrete)Wood chip retrieval from storage(for 150 kW)Wood chip retrieval from storage(for 650 kW)

200 / m6.6157.485

Storage silo for pellets (no fuel

retrieval necessary)

104 / m

For simplification use the following figures for annual operation related costs:

Biomass OilElectricity costs 0,6 / kW 0,5 /kWPersonal costs 10 / kW 0Chimney sweep 300 300

Maintenance, service 4 /kW 2 /kWInsurance 2,5 /kW 1 /kW

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4 Subsidies

Typical subsidies for Austria are 30% of investment costs

5 Fuel costs

For this example the following characteristic figures for Austria should be used:

Fuel kWh / lor.

kWh / kg

Euro / liter, orEuro / kgexcluding

VAT

Cent / kWhexcluding

VAT

Light fuel oil 10 0,38 3,8Quality forestry woodchips (35% humidity)

3,2 0,060 1,9

Industrial wood chips(40% humidity)

2,8 0,040 1,4

Wood pellets (8%humidity)

4,7 0,123 2,6

6 Fuel storage

For pellet heating systems the storage of annual demand can be economic as pellet costs insummer can be up to 20% lower than in winter. For larger boilers and the use of wood chipsit is not economic to store the entire annual demand. It should be possible, however, to storeat least 1.5 truck loads of fuel to assure economic transport. As a minimum fuel demand for 1week of operation in full load mode is often mentioned: The adequate fuel volume will needto be calculated for each case depending on the local availability of fuel and the priorities ofthe customer.

Truck capacity for blowing in of pellets: approximately 12 tons or 18 m pellets Truck capacity for pellets (dumping) . 20 tons or. 30 m pellets Truck capacity for wood chips (dumping) 80 m3

The most common storage systems are underground concrete storage, where fuel can bedumped and outdoor metal silos (as typically used in construction industry for concrete etc.)It should be considered that a storage, into which fuel is dumped, usually cannot be used toits full capacity. The amount of fuel fitting into a storage depends on the geometry of thestorage and the location of the opening. In this case it should be considered that the storageroom can be filled up to a maximum of 75%.

In the Excel sheet the costs for fuel storage have to be entered under construction costs. It isconsidered that in this case no construction costs are necessary to adapt the heating room.The costs for improving the chimney can be entered in the line installation costs as the latterare included in the boiler costs and must not be entered separately.

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7 Selection of biomass boiler

Different biofuels have quite different combustion properties. It is of decisive importance tohave a clear definition of fuel when selecting boiler manufacturer or a certain type of boiler.

Potential future changes in fuels should be considered in advance. This is the most importantprecondition for the selection of the proper wood boiler and for secure and problem freeoperation.In general the following types of boilers are available:

Wet wood chips (>40% water content): moving grate boiler Dry wood chips (

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pellet costs in summer justify the establishment of fuel storage for the entire annualdemand. In this case assume fixed other costs (underfeed stoker) and check theimpact of fuel storage size on heat costs.

3. Calculate the volume and costs of a heat storage tank and check the influence ofheat costs. Assume in this case (simplifying) a linear decrease of boiler costsbetween 650 kW and 150 kW. Assume also that the heat storage tank increases theannual efficiency of the plant from 75% to 80% and reduces the costs for service andmaintenance by 50%.

4. Compare the heat costs depending on the selected fuel - take into account thedifferent boiler types needed to match the fuels and the different costs for the fuelstorage.

5. Analyse the competitivity of biomass in comparison to oil and gas assuming that onlyin the 650 kW case a new oil storage has to be established.

6. How does the subsidy affect the economics of the plant?7. How would a doubling of fuel costs affect (biomass costs, oil costs) the comparison of

economics?

Develop a most economic and a most reasonable scenario for biomass heating to yourmanagement and present the results of your analysis in approx. 10 power point sheets.

Acknowlegement

The development of this case study was actively supported by the following companies: Fa.kowrme Schrkhuber www.oekowaerme.at , Fa. Binder Feuerungstechnik www.binder-gmbh.at and Fa. ACETEC www.acetec.at