Wood Biomass CHP at the sub 1MWe scale. Dr David Telford Director Energy and Sustainability Division hurleypalmerflatt

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1 Wood Biomass CHP at the sub 1MWe scale Dr David Telford Director Energy and Sustainability Division hurleypalmerflatt

2 Wood as an Energy Source Renewable Resource Indigenous Supply Could be sustainable Proven use of biomass for heating But Very limited technologies and reference plants for CHP/electricity generation at scale needed

3 Good Quality Biomass CHP supported by legislation Exemption from the Climate Change Levy (CCL) on all fuel inputs to and electricity Eligibility for Enhanced Capital Allowances (ECA) on Good Quality CHP systems Dedicated biomass fuelled CHP earn double ROCs/MWh May get RHI on part of the plant

4 Wood as a fuel Net Calorific Value (NCV) by mass GJ/tonne NCV by Mass kwhr/kg Density kg/m3 Energy Density by volume (kwhr/m3) Fuel Relative to Oil Wood chip (30% Moisture Content) % Air Dry Logs ( 20% Moisture Content) % Wood pellets ( <10% Moisture Content) % Heating Oil % LPG %

5 WOOD CHP Options Considered Wood Gasification Syn gas to gas-fired prime movers Mass burn Stirling Cycle ORC ( Organic Rankine Cycle) Hybrids Note: Conventional Steam plant based on mass burn of wood is also possible but was discounted due to operator skill base and issues with scale and flexibility. FUEL GAS HEAT Use Internal Combustion External Combustion Generator Power Use

6 Gasification

7 Gasification This wood gasification system requires a very specific fuel type. Clean factory or industrial off cuts with no fines and a moisture content of less than 10%. Gas produced is a mixture of Hydrogen and Carbon Monoxide. Gas is then burnt in a diesel engine/ alternator set converted to spark ignition. Waste heat from exhaust and gasifier is captured and used to provide heating Up to 1:2 Power to Heat ( ie 1 Kg Wood = 1 kwh Electricity + 2 kwh Thermal)

8 Some Issues with Gasification - for this application Gas composition can be variable Gasifiers can produce tar and foul gas cleaning plant or boiler tubes Not good with variable quality and moisture content wood Variable quality gas Many examples of plants abandoned several years after commissioning

9 External Combustion Sterling Cycle ORC

10 Stirling Cycle Stirling Cycle is a closed cycle technology which uses an external heat source (in this case burning wood) to produce electricity. Many different experimental configurations are possible. UK British Gas-Microgen. Research abandoned by British Gas in spring 2007, used SunPower free-piston/ linear alternator technology. Small scale hermetically sealed linear Stirling engine

11 Stirling Engine Suppliers UK British Gas-Microgen. Research abandoned by British Gas in spring 2007, used SunPower technology. Microgen Engine Corporation uses Sunpower free piston technology. E.ON (was PowerGen) (uses Whispertech technology) Baxi Ecogen uses SunPower free piston engine. Disenco Energy uses a beta type Stirling engine based on a Sigma Elektroteknisk design with rhombic drive. New Zealand Whispertech Most small scale ( 1 2kWe) Except: Denmark Stirling Danmark Designed for biomass Austria Stirling Power Module GmbH Designed for wood pellets. USA Infinia Corp Germany Study Group Stirling Wood fired Beta engine.

12 Characteristics Name Type Nominel Electrical Capacity Nominal Heat Capacity Working Gas Detail Engine Model SD4-E 4-Cylinder Alpha Type 35 kwe 90 kwth Helium Engine Electrical Efficiency 28% Design Service Intervals Lifetime Weight 4,000-6,000 hours 100,000 hours 2.5 metric tons

13 Organic Rankine Cycle (ORC) Similar to conventional Steam turbine, except that the water/steam working fluid is replaced by a refrigerant/ organic oil. This allows small scale turbines/ expanders to be used and reduces the need for high pressure steam plant. Working fluid is selected for the pressures and temperatures required ORC generators are generally available in capacities of around 10kWe to 2MWe and are well suited to part load operation, giving increased flexibility. Efficiencies of around 17% to 18% can be expected, (4:1 5:1 Heat/ Power).

14 Suppliers Only a few companies make and manufacture ORC turbines A number of branded ORC units use either: Infinity turbines Pratt and Whitney Bespoke designed Scroll expanders (Enefcogen & Air Squared) Converted refrigerator compressors (running as expanders). Infinity turbine Air squared Expander/ Alternator Enefcogen Scroll Expander

15 Turboden Pratt and Whitney a large scale solution BSkyB campus in Hounslow, West London, - 32 tons of wood chips per day 1 MWe ORC turbine. 4 MWth BAA Airports Limited,London Heathrow 1.8 MWe of electricity and 8MW of thermal heat and cooling to Terminals T2a and T2b, and heat only to Terminal T5. Girvan Land Energy wood pellet plant - 2MWe Turboden Plant. (waste heat is used to dry wood and produce pellets).

16 Selected Solution: Eneftech Packaged Unit Conventional Biomass boiler ORC Unit Optional Solar Thermal Collector

17 Enefcogen in Swimming Pool Application Biomass Boiler

18 Solution 1 ORC based on Enefcogen technology Conventional Biomass boiler with hot oil heat exchanger as heat source Packaged expander/ Alternator set External pool as heat sink for condenser Advantages Modular, separates heat from power solutions Selection of robust proven technology for biomass boiler Packaged ORC plant for low maintenance Issues Poor heat to power ratio High capital cost compared to diesel or Gas CHP Requires back-up heat and power

19 Solution 2 Gasification & Stirling Engine DK mounted on boiler The hot heat exchanger in the four-cylinder 35 kwe Stirling engine is designed specifically for utilisation of biofuels. Four heater panels form a large combustion chamber where narrow passages are avoided in order to adapt solid fuel combustion gases. The heat transfer rate is kept at around 60 kw per m2 corresponding to common practice in steam plants for biofuels

20 Selected Solution: Stirling DK Gasifier / Stirling Engine

21 References Suppliers Orc turbines Gassifiers Large Scale Packaged Plant ORC Case Studies

22 Contact details David Telford Director Energy & Sustainability E: Glasgow Office: 204 West George Street Glasgow Scotland G2 2PQ T: