Viessmann- Boiler Options Case Studies

Boiler Options - Case Studies - Biomass - Wood Waste - Shared Heat Network

Viessmann looks at two contrasting applications in the UK where biomass is simply good common sense.

As with all types of renewable energy, there are pros and cons to going down the biomass route. Biomass can play a major role in helping to reduce carbon footprint while making use of resources that would be otherwise treated as waste and sent to landfill. Wood is affordable and not subject to wide price fluctuations. Acquiring it can contribute to the local economy that supplies it. On the other hand, the initial capital costs of installing the system are high and the space required to store, yet alone process, the wood is no small consideration.

While biomass may not be coming to a cul-de-sac near you anytime soon, there are notable applications where any other fuel type would seem non-sensical. These case studies explore installations at IKEA and Kielder District Council where Pyrot and Pyrotec systems supplied by Viessmann’s KÖB brand have helped boost a retailer’s recycling and green credentials, and created a new network for an off-grid energy community.

IKEA: pioneering biomass in the UK retail sector

When IKEA made the decision to purchase an automatic feed, woodchip, central heating system to provide warmth and hot water for its new Milton Keynes retail store, it became one of the first multinational companies in the UK to install a biomass boiler on purely commercial terms. The Swedish furniture company wanted to recycle 90 percent of its in-store- generated waste as well as to save carbon and reduce dependence on fossil fuels. It selected a KÖB Pyrotec 950 kW biomass boiler to be the primary heating plant for the store and a KÖB Pyrot 220 kW wood waste boiler to burn a proportion of its clean pallets and packaging. The result is secure, locally-sourced fuel at a competitive price together with estimated carbon savings of over 1500 tonnes per year.

Biomass boiler

The KÖB Pyrotec 950 kW biomass boiler was selected as the main heating boiler. Fitted with automatic ignition, cleaning and de-ashing equipment, it is capable of burning woodchip fuel of up to 50 percent moisture content. A 120 cubic metre fuel store with walking floor extraction was located under an HGV loading deck where it would not interfere with the retail operation. The fuel is delivered from the store to the boiler by a series of augers. The boiler modulates its output to match the heat load of the building and uses a pneumatic self-cleaning system and automatic de-ashing to an 800 litre wheeled bin so routine maintenance is minimised. It is shut down for an hour-long manual cleaning process once a month.

Wood waste boiler

A KÖB Pyrot 220 kW wood waste boiler was installed as the lead boiler. It came with a shredder, magnetic separator conveyors and a silo as a complete package to recycle clean wood waste from pallets into useful heat for the store 24 hours a day. The boiler is capable of burning just under 45kg per hour of clean wood waste. The silo is capable of storing over 50 cubic metres of wood so that the shredder may be run occasionally with a secure stock of wood fuel available.

The KÖB Pyrot 220 boiler came complete with flue-gas recirculation to minimise emissions, automatic ignition, cleaning and de-ashing, in common with most other boilers in the KÖB range. A flue cyclone has also been fitted to ensure minimum particulate emissions from the potentially dusty fuel. The wood waste boiler burns up to 7.5 tonnes of fuel per week producing around 24MWh of heat.

Community pay back in Kielder

Tynedale Council turned to wood after looking for a new heating and hot water supply for the remote, forestry village of Kielder in Northumberland. Inhabited by 200 people, the village – heated previously by oil or solid fuel stoves and open fires – has several individual homes, a petrol station, village shop and pub, as well as communal buildings such as the Youth Hostel and the visitor centre at Kielder Castle. The Council wanted to make sure that while local resources should be used to heat a majority of buildings, it would be done in an energy-efficient way with low emissions.

It was decided to install a form of central heating novel to the UK: a shared heat network fuelled by wood. A local fuel stockpile store, which is filled up three or four times a year with specially dried and chipped logs (wind-blow and low value timber), was specially designed and built in the Forestry Enterprise Depot. Inside the boiler house, a ‘walking floor’ moves the woodchips from the storage area to the augers, which then convey the woodchips into the boiler. The KÖB Pyrot’s output is 300kW, with an efficiency of 87 percent (measured as heat output to woodfuel energy input). It has a special rotating firebox, designed to burn all kinds of dry and damp wood fuel (chips, sawdust, shavings, pellets, briquettes, forestry wood shavings).

Hot water leaves the boiler at 85°C and is piped to surrounding buildings where heat exchangers transfer the energy into domestic heating and hot water systems. Over 950 metres of super-insulated plastic heat pipe connects each building to the boiler house. The water returns from the building a little cooler, and is reheated by the boiler before being pumped around the system again. The boiler produces very little noise, smoke or ash. Visitors sometimes cannot even tell when it is running!

Kielder Community Enterprise Ltd. has been established as a community- owned energy service company or ‘ESCo’, providing a permanent source of local employment, and sends users monthly heating bills (calculated by meters). Emissions from the chimney are mainly composed of water vapour: total emissions are less than a single household coal fire. The few wheelbarrow-loads of ash produced each year are used as a fertiliser to mix with compost for the village gardens and allotments. Compared with alternative fossil fuels, the Kielder district heating system saves about 57 tonnes of carbon dioxide emissions per year. Any greenhouse gas carbon emission is balanced by forest re-growth.