Quality management in local biomass district heating systems Impressions from the technical advisory visits to UK and Slovenia

Slide 2 Bioheat Žetale – Starting situation -Žetale is a small municipality in the east part of Slovenia with around 1500 inhabitants -12 farmers decided to invest in a wood biomass heating system and established a cooperative -They prepared a survey from which they found out potential customers and their energy needs. On the base of the survey they selected a location for the district heating plant.

Slide 3 Bioheat Žetale – Let´s start! 1.Find investors / operators of the biomass district heating system 2.Inform people about project activities (Workshop) 3.Determination of the heat demand of the total densely populated catchments area 4.Creation of a scale plan, where the individual objects are identified by their heat demand 5.Creating a rough study, in terms of economic viability and feasibility of the project 6.Discussions with potential investors 7.Discussions with potential customers, to inform the public about the concrete project activities (e.g. organize information meetings)

Slide 4 Feasibility study Analysis of future heat sales Heating load and hours of full load operation Investment costs Boiler, installation, construction work, district heating grid, heat transfer stations, planning, amount of own work, boiler room, storage Operational costs Wood fuel Maintenance, service contract, personal, chimney Capital pay back, automatic alarm system, insurance, accounting & taxes Calculation of heat price

Slide 5 District heating grid

Slide 6 Customers of heat consumption

Slide 7 Investment costs depends… Is there an existing boiler room? Is the boiler room large enough to accommodate a wood boiler? Can the wood fuel be stored in the existing building? Is it possible to attach an external fuel storage? How can woodchips be delivered? (Enough room for a truck to turn?) Need to put district heating pipes in streets (expensive) or soil (cheap)

Slide 8 Bioheat Žetale – Starting situation

Slide 9 Bioheat Žetale - Specific heat cost & annual total costs

Slide 10 Distribution of the specific heat costs with subsidies

Slide 11 Bioheat Žetale – Amortisation of the project

Slide 12 Ecological / efficiency evaluation of the project

Slide 13 Discussion point: Boiler size Which solution is the best – one or two boilers ? the installation of 2 x 200 kW would recommend instead of 1 x 400 kW, but this increases the investment costs (-> in the summer only the 200 kW boiler is in operation -> more full load hours -> less emissions and less wood fuel demand) In contrast to the 200 kW boiler, a 400 kW boiler is available in an industrial version, which can also burns quality fuels with less quality easily The decision for a boiler should also be made on the basis of the available fuel range

Slide 14

Slide 15 Criteria for a good boiler References in practical applications High efficiency (>90%) Low emissions Automatic cleaning of heat exchangers Automatic ignition Automatic ash removal Available service (24 h/d, 365 days/a)

Slide 16 Boiler load during the heating season % of full capacity Heating days

Slide 17 Planning, tender and purchasing Correct dimensioning of boiler, possibly peak load and backup boiler Heat storage tank for load management and to cover peak load in the morning hours Use standard components – no special solutions Plants up to 150 kW with competent installer, no tenders

Slide 18 Heat storage tank Higher efficiency of boiler operation Fuel savings Lower emissions Better heating comfort No tar depositions in chimney and boiler due to low load operation

Slide 19 Diskussion point: Heat grid I Heat grid - Plastic or iron: The decision is a question of a price - Plastic tube is limited due to the pressure and temperature (manufacturer) - At high temperature and pressure decreases the time life of the network - Heating networks should not be dimensioned too large, it increases the pump electricity costs which causes heat losses

Slide 20 Always have an overall concept in mind, Always think on a later extension of the network (the heat network must be planned for the overall concept) e.g. costumers decide for local heat after his existing heating system no longer work e.g. higher prices for fossil fuels leads to a higher increase of demand Attention: a lot of houses invest in thermal insulation (less heat demand in the future) Diskussion point: Heat grid II

Slide 21 District heating grid: Important technical specifications Significant temperature difference between out flowing and back flowing water (min. 30 °C) Temperature of backflow < 40 °C most of time hydraulic regulation of heat distribution system of customers more than 900 kWh of heat sales per meter of grid length High quality insulation of pipes Small diameters of pipes

Slide 22 Discussion point: Fuel quality Fuel quality 2x 200 kW plant: water content up to 35%, max. size pieces G50 mm (ÖNROM, G50=cross section of the wood chip is > 5 cm²) 400 kW plant: water content up to 50%, size pieces > G50 mm

Slide 23 Basic issues Fuel quality is THE key for flawless plant operation, especially smaller plants are not suited for wet fuel ! Wet fuel (water content > 35%) can cause combustion problems, smoke emissions and energy losses Large pieces of wood can block the screw feeder and stop operation

Slide 24 How to achieve high quality fuel ? Before chipping: ideally 1 summer storage of trees in a pile Use suitable wood types Reduce impurities to a minimum (sand and soil, stones, metal,...) Sunny and wind exposed storage area Short storage periods, as short as possible and as long as necessary Chipper well maintained (sharp blades)

Slide 25 Discussion points: Back-up system Options for a back-up system: 1) In variant 2 x 200 kW you have a boiler automatically as a reserve, provided that the fuel supply is disconnected (2 space host systems). 2) For a short time (3 - 5 h), the buffer offset a loss 3) Implement the existing gas heating system of the school into the biomass heating plant as a back up system (e.g Zetale)

Slide 26 Discussion points: Year-around system Year-around system ? The heating is carried out at newly installed district heating systems almost exclusively in the year-around operation The comfort for the consumer is much higher The heating plant can also be extended to a solar system A year-around operation has higher net losses, because the network must be maintained all year

Slide 27 Diskussion points Wood chip storage / delivery ? -In the coldest month you need about 15% - 20% of the total annual demand. A to small wood chips storage in practice leads to problems. -The wood chips delivery is done either through central wood chips storage or direct from the participating farmers. -It is recommended to settle the wood chips by weight and water content and prevent future problems.

Slide 28 Wood chip delivery by conventional hanger: simple & cheap

Slide 29 Example Storage next to boiler room Storage in existing cellar with a storage filling screw

Slide 30 Examples Storage above the boiler Storage above and beside boiler, fuel retrieval on boiler level

Slide 31 Biomass district heating plants Lessons learned - main technical deficiencies are: The heat demand of consumers is overestimated The pipeline system is oversized Size of the storage is much bigger than necessary Low utilisation ratio of the wood boiler Fuel quality does not meet the quality requirements for the Installed biomass boiler

Slide 32 Financing of Wood Energy Contracting Projects little loan fraction 1/3 own capital, and services on own account 1/3 subsidy 1/3 connection fee

Slide 33 Just little building measures necessary (adaptation of existing heating rooms and fuel wood storerooms) low conduction losses (less than 20%), low costs for pumping electricity small and straightforward projects with low investment costs and risk reasonable alternative to long distance heating projects and individual equipments Advantages of Wood Energy Contracting Projects

Slide 34 Biomass district heating

Slide 35 Thanks for interest! Contact Thomas Loibnegger Energy and Biomass T: Chamber of Agriculture and Forestry Styria Hamerlinggasse Graz - Austria