Damian Shevloff, Cogenco, UK
The use of alternative fuels is growing. With take-up in Europe demonstrating what can be achieved, and driven by developments in carbon-neutral technology, more UK organizations are recognising the value of bio-fuelled, cogenerated on-site power.
Combined heat and power (CHP) plants are often fuelled by natural gas, which is clean, consistent in quality and often cheaper than alternative fuels. However, a CHP plant can also operate on biogas, landfill gas, liquid gas, propane, biomass, diesel and bio-diesel. The commitment of countries such as France, Germany and Italy to reduce carbon emissions and improve energy efficiency levels has led to the growing use of ‘waste’ and biomass fuels. On-site CHP and waste-to-energy CHP, in particular, are a viable route to similar energy efficiency, cost reduction and environmental improvement for the UK too, because natural energy and carbon efficiencies embodied in gas or oil-fired CHP are enhanced with the use of a carbon-neutral fuel.
DRIVERS OF THE EUROPEAN SHIFT CHANGE
The growth of waste-to-energy and bio-fuelled CHP in Europe are being driven by the escalating price of fossil fuels, the need to recycle and the need to reduce carbon dioxide emissions. The ‘spark gap’ (between gas and electricity prices) has driven more organizations to turn to more efficient and cost-effective means of on-site energy generation. Coupled with this is a growing awareness of waste management as a key business operation, fundamental to cost efficiency. Minimizing waste to landfill by utilizing on-site by-products to fuel cogeneration plants provides a solution that reduces reliance on carbon fuels and simultaneously diverts a waste stream from landfill.
A robust approach to organizational corporate responsibility has significant value for public relations too. The on-site use of energy generated on or close to its point of use, via CHP, delivers multiple benefits: low cost heat and electricity; enhanced environmental ratings, which increases further when using bioenergy; lower operating costs and more attractive rental prospects; lower susceptibility to energy price fluctuations; a stable and uninterrupted energy supply; lower carbon footprint; and overall increased asset value.
Legislative drivers are also playing their part. Europe is responding to some measures not yet in place in the UK. The most common point of comparison is the favourable rates for renewable energy under feed-in tariffs (FiTs). For example, the current Spanish feed-in tariff, Royal Decree 661/2007, recognises cogeneration systems that feed surplus electricity to the grid. Organizations can claim a maximum FiT of €0.1329/kWh ($0.1762/kWh) during the lifetime of such a system.
UK DRIVERS FOR WASTE-TO-ENERGY ON-SITE COGENERATION
The UK’s FiT programme will come into force in April 2010 under a ‘clean energy cashback’ policy. A key feature of the UK’s FiT programme is provision of power from CHP plants. Sites where CHP is used to deliver heat and power directly to its point of use can avoid the Climate Change Levy. Meanwhile, UK organizations are increasingly looking to improve their carbon footprint in order to gain better energy performance certificates (EPCs) and display energy certificate (DEC) ratings.
In addition, under the Renewables Obligation scheme various green energies attract renewables obligation certificates (ROCs), including biogas from anaerobic digestion (AD), biomass, hydro electric, tidal power, wind power, photovoltaic cells, landfill gas, sewage gas and wave power. Co-firing biomass plants are also eligible. Each of these options is supported to various levels due to differences in their economic viability.
Most buildings are obliged to show DECs and EPCs. Since October 2008, all public buildings over 10 000 m2 in the UK have been required to show a DEC outlining the structure’s previous three years’ energy use. Equally the sale, rent or construction of new buildings will trigger the requirement for an EPC. Finally in the UK, the Carbon Reduction Commitment (CRC), coming on-line in April 2010, is pushing organizations outside of the traditional remit for CHP (industry and healthcare), such as retail, leisure and hospitality, look to on-site cogeneration as a means of improving carbon performance, with savings to be gained under the CRC.
LESSONS FROM EUROPE
The use of used and recycled wood as a biomass fuel for on-site CHP has been pioneered across Europe, with far-reaching implications for the future of UK on-site power production too. Used wood, including all soft and hard wood products such as pallets, off-cuts, boxes, packaging, cases, chipboards and plywood, are removed from the usual route to landfill.
Instead, these materials are graded and processed to form a wood bio-fuel that is then used directly in biomass CHP plants. At Quarona in Italy’s Piedmont region, Dalkia manages on-site thermal installations that provide heat and power directly to the two primary schools and crèches, in addition to residential buildings across the region.
The installation comprises a 980 kW wood-fired boiler, meeting a total energy requirement of 1200 MWh per year. In the production of electricity and heat, the boiler burns 500 tonnes of waste wood pellets a year.
PannonPower, a subsidiary of Dalkia, is operating Hungary’s largest biomass plant at Pécs. Wood from logging operations in the region accounts for 70 per cent of the fuel and the unit generates 50 MWe. Most of the fuel is sourced from trees that are deemed unsuitable for other applications – for instance those which are diseased or too warped for working – while the remaining 30 per cent of fuel is derived from wood waste and agricultural by-products. An on-site chipper processes the wood to form pellets for burning. The boiler is fed by ground-level hoppers connected to an underground conveyor belt. The two conveyors that supply the boiler operate alternately so that maintenance work does not hold up production.
|An engine-based CHP unit which allows the conversion of waste into valuable energy|
As a result, the boiler is fed continuously by either of the two conveyors, at a maximum rate of 100 tonnes per hour. The biomass boiler uses fluidized-bed technology. Inside the boiler, at the base, 120 tonnes of sand are fluidized, or put into suspension, by 2000 blowers that inject air. With the boiler temperature at 850 °C, the chips are instantly transformed into charcoal. This charcoal then burns more slowly to produce steam at 540 °C and 98 bar.
This high pressure, high temperature steam is supplied to the production unit’s turbine. The turbine produces electricity via the generator, as well as a small amount of heat, which is sent directly to the district heating network. During periods when heating is not needed, the unit supplies the city of Pécs with domestic hot water. The Pécs plant is currently equipped with three operating boilers: a gas-fired boiler that powers a 38 MWe CHP turbine, a gas-fired boiler that powers a 35 MWe condensing steam turbine (100 per cent electricity) and a wood-chip biomass boiler that powers a 50 MWe condensing steam turbine (100 per cent electricity). The plant has a total heating capacity of 313 MWth. Of the three units in service, two are gas fired and one is biomass fired.
With rising gas prices, Dalkia is switching the remaining units to biomass-fed CHP too. The new facilities will run on energy crops grown on-site and, in order to expand the range of fuel options available to the plant, Dalkia is developing a poplar plantation nearby with the aim of generating electricity from dedicated energy plantations.
In Litesko, Lithuania, another subsidiary of Dalkia, has installed five wood burning boilers with a combined power of 20 MW, providing up to 50 per cent of the total heating and sanitary hot water needs of Kelme, Kazlu Ruda, Kybarti, Palanga and Telsai. This far reaching scheme optimizes the existing energy networks and secondary installations such as substations, insulation, recycling, regulatory and automation systems, as well as the renovation of the water treatment system. Likewise at Vilnius in Lithuania, renewable energy is being produced on-site for 140 000 homes using wood chips in a 12 MWe CHP plant. Hot water, heating and electricity is provided for inhabitants at a lower cost than grid-fed power.
|Modern CHP plants can be monitored and controlled remotely, allowing flexibility for the employees and employers|
The benefits of these examples are tangible. The on-site applications – schools, hospitals and homes – are assured of stable energy prices, while the systems use local and sustainable resources in the form of waste wood that is removed from the waste stream.
EARLY ADOPTERS IN THE UK
The UK is slowly switching to the benefits that the rest of Europe has known for some time. Now the environmental performance of on-site generation through CHP plants is being enhanced by technologies that enable the use of discarded materials to be burnt in the process of generating electricity. This is providing a viable option for organizations in the UK considering on-site cogeneration to improve environmental performance and deliver energy cost efficiencies.
While CHP has been widely recognized by the large scale industrial and healthcare sectors in the UK for some time; the market is now evolving to generate heat and power on-site not only from biogas created through AD, but also from landfill gas, bio-liquid and biomass too.
|Improved environmental performance is enabling the use of discarded materials to be burnt in CHP plantsa|
In a world first, drinks manufacturer Diageo is building an advanced bioenergy plant on-site at its new state-of-the art distillery in Roseisle. This is planned to produce around 12.6 million litres of malt whiskey each year. Dalkia is designing, installing and operating the plant, which will utilize a by-product, from the production process as biofuels to generate steam and recover water.
The draff consists of spent grain and potale, the wash and steep water from the distillery. It is planned that the plant will dry and burn around 33 800 tonnes of draff in the biomass boiler, while 338 000 tonnes of potale will be fed through an AD to produce biogas for the boilers. The plant will also recover some 300 000 m3 of water for use in non-process related activities.
This site represents a genuine green energy solution that will reduce Diageo’s reliance on carbon fuels and cut emissions by 22 000 tonnes per year.
Diageo has also recently begun work to construct a bioenergy plant at its in Cameronbridge Distillery in Fife. This £60 million ($92 million) facility has been designed, is being constructed and will be operated and maintained by Dalkia. It will combine AD technology and biomass conversion of the spent grain, used in the production of grain spirits, to provide 98 per cent of the thermal steam and 80 per cent of the electrical power requirements across the site. As a result Diageo expects the Cameronbridge site’s annual carbon dioxide emissions will be reduced by some 56 000 tonnes.
This specialist services package is believed to be the largest single investment in renewable technology by a non-utility company in the UK; the range of this scheme would usually require the input of several expert outsourcing partners. By combining the distillery’s recycling policy, its need for electricity and its specialist plant, Dalkia and Diageo have together delivered a truly integrated energy management and specialist services package. The use of by-products on-site as biofuels negates the need for transport previously needed to move waste materials off-site.
It is not only in food and drink production on-site bio-fuelled CHP is making its mark on the UK’s energy landscape. In the retail and distribution sectors Dalkia is working with Tesco to halve its carbon emissions from its buildings by 2020. Alongside this, Tesco’s creation of a £100 million Sustainable Technology Fund to support large-scale carbon reduction technologies at stores, distribution centres and throughout the supply chain has seen a significant investment in on-site CHP and trigeneration for its UK stores, with 33 CHP plants installed and operational during 2009.
Marrying CHP and trigeneration supplied by Dalkia with other technologies, Tesco saved 66 000 tonnes of carbon from its stores in 2008 alone. With a proven track record across Europe, waste-to-energy cogeneration represents a viable route by which UK organizations can realise similar energy efficiency, cost reduction and environmental performance improvements. Utilizing a sustainable and carbon-neutral fuel source is a realistic model that can deliver results for large and small-scale applications where CHP is an option.
ABOUT THE AUTHOR
Damien Shevloff is head of sales at Cogenco, a Dalkia company, based in Horsham, West Sussex, UK.
This article first appeared in Power Engineering International’s sister title, Cogeneration & On-site Power Production
Dalkia and bioenergy
Dalkia currently operates 1230 CHP plants across Europe, representing a generation capacity of 4920 MWe. The company already delivers 250 MWe capacity through CHP technology in the UK, and over 1500 MW of energy from renewable sources internationally, with over 100 biomass plants across the world. Dalkia Bio-energy is a new business operation and an integral part of Dalkia’s energy services solution. Dalkia Bio-energy processed almost 100 000 tonnes of biomass wood pellets by the end of 2009.