Thursday 28 th and Friday 29 th September 2006 Imperial College London, South Kensington Campus, London SW7 2AZ
Imperial College London Decentralised Energy Systems Matthew Leach (contributions from Adam Hawkes) m.leach@imperial.ac.uk www.iccept.ic.ac.uk Imperial College Centre for Energy Policy and Technology Imperial College London
Mission ICEPT Director: Professor Peter Pearson Deputy Director: Dr Matthew Leach Research & policy advice at interface of energy policy & technology An Interdisciplinary Centre Collaborating with Imperial s Energy Futures Lab and with UK & international researchers Outputs Research findings Evidence-based technology & policy review Postgraduate training strong PhD programme MSc in Environmental Technology: Energy Policy Option 2
Presentation outline What is Decentralised Energy? Decentralised Energy at Imperial Why interest in DE? ICEPT s work: illustrative examples on micro-chp Conclusions 3
Conventional power system Industrial consumers Distribution network Central power producers Residential consumers Source: based on Ofgem(2002) 4
With decentralised energy + cogeneration =>consumers & producers Active distribution network + embedded generation + microgeneration =>consumers & producers Source: based on Ofgem(2002) 5
Importance of networks, components and people One vision of the future of power systems (analogy to internet evolution:- Source: Rebecca Willis. grid 2.0 the next generation. Green Alliance, 2006 6
Decentralised Energy components Source: adapted from Mariyappan (2003) (a) Power/heat conversion (both grid-connected and off-grid ) Fossil fuelled (some with potential for bio-fuel substitutes) Relatively large scale, conventional technology, eg: Combined-Cycle Gas Turbine (35 MW 400 MW) Internal Combustion Engines (5 kw 10 MW) Smaller scale, eg: Stirling Engine (1 kw 10 kw) Microturbines (35 kw 1 MW) Fuel Cells: Solid Oxide or Proton Exchange (250kW 5MW; 1kW 250kW) Renewables, eg: Small Hydro; Micro Hydro (1 MW 100 MW; 25 kw 1 MW) Wind Turbines(200 Watt 5 MW, to GW arrays) Photovoltaic Arrays (20 Watt 100 kw) Biomass, e.g. based on gasification (100 kw 20 MW) (b) Energy storage devices (c) Demand side: information systems, intelligent control 7 (d) Associated infrastructures (notably active electricity distribution networks)
Decentralised Energy at Imperial Strong technology programmes in many departments (eg Fuel Cells, PV, wind, bioenergy, waste-to-energy, ) Department of Electrical and Electronic Engineering: strong group on power system control, DG integration and future of networks Centre for Energy Policy and Technology (ICEPT): focus on techno-economic, environmental and policy analyses of emerging energy options (eg H2, fuel cells, bioenergy, building integrated and off-grid renewables, and decentralised energy specifically) Particular areas of interest to ICEPT Modelling approaches, and sensitivities of optimum design to economic, market and environmental factors Demand-Side participation Micro-Grids and community heat networks Small scale waste to energy systems (eg contacts with Ebara corp gasification) Valuation and risk-management of decentralised energy investments Transitions to DG power systems and scenarios Policy aspects 8
Why interest in Decentralised Energy (globally)? 9 Technology New, smaller, conversion devices Can help overcome T&D network constraints Stimulate development of active networks Environment, economics Some options inherently low carbon (eg renewables) Can facilitate use of cleaner fuels (eg local wastes or biomass) Avoidance of transmission losses * Opportunity to capture waste heat for local heat loads Facilitate closer end-user engagement with energy Contribution to wider transition to low carbon future Economics, commercial Low capital, fast revenue stream = lower risk modular investments Value of flexibility, adaptability and diversity in a competitive market Integration of electricity, gas & heat suppliers/markets Underlying need for new power investments, globally Security of supply Possible improvement in power quality and security of local supply *
Gas Industry Elec. Transport Resident. Petrol. Gas to heat houses 10 Power generation conversion losses
WADE (2003) 11
Constraints facing Decentralised Energy (in UK) Current market structures and rules Some high technology costs High gas prices Planning and connection constraints and public perceptions Network integration: capacity to accept is limited and not always where needed 12
Growth in electricity generation from renewable sources since 1990 (Source: adapted from DUKES 2002 2005) 15 13 2015
Capacity [GW] Market size - Global DG capacity (< 10 MW) by market segment 200.0 180.0 160.0 140.0 120.0 100.0 80.0 60.0 40.0 20.0 0.0 2005 2010 2015 2020 Shift away from centralised power by utilities Extended electrification to off-grid locations Residential / community applications Commercial applications Industrial applications <10MW Key Findings Possibly very significant shift in emphasis on the part of utilities to distributed power Large DG growth expected in industrial applications and extended electrification DG penetration in commercial and residential is lower, but characterised by a large number of smaller units Source: Imperial College / E4tech Ltd 14
Residential Micro-CHP Stirling engine, ICE, Solid Oxide Fuel Cell, PEM Fuel Cell Source: Ballard Source: WhisperGen Source: Hexis 15 Source: Baxi
System Diagram Fuel Input Fuel Conditioner Solid Oxide Fuel Cell Heat Recovery System Afterburner (burns excess fuel) Hot Water Storage & extra Boiler Heat Load Electrical Load Fuel Flow Heat/power Flow Losses Grid Power 16
Stack and BOP model Pre-reformer Fuel feed Mixer Air feed Fuel pre heater - Anode side Cathode side + Burner Air blower Steam generator Air pre-heater Power Water 3 phase AC 17 Hot water Waste heat recovery Cooling water Exhaust gas
Optimisation Model Applications How to model residential CHP applications Key economic drivers for SOFC-based technology Influence of ramp constraints on economic and environmental outcomes Synthesise a least cost operating strategy How best to meet thermal demand (eg value of thermal storage) Capacity credit of micro-chp: % of installed capacity that will reliably reduce peak system demand Relative performance of micro-chp and community scale (Next) Influence of changing patterns of thermal demand 18
Input data time-step assumptions Hourly Data Five Minute Data 140 Electrical Power Demand 30 Electrical Power Demand 120 25 Power Demand (kwh) 100 80 60 40 20 0 0 5 10 15 time (hours) 20 25 Power Demand (kwh) 20 15 10 5 0 0 5 10 15 20 time (hours) Carbon emissions reduction is overestimated by analyses using coarser temporal precision by up to 50%, and economic case overestimated by around 10%. 19 Coarser precision overestimates export of low-carbon electricity, and underestimates import of high-carbon grid power.
SOFC for DG in UK Ceres Power, a SOFC tech. company (& Imperial spin-out) recently won the Carbon Trust innovation award in the UK. SOFC has the potential for a relatively low cost/kw installed Fuelled by natural gas or hydrogen rich fuel Carbon-efficient technology, very low NO x, very low SO x Research underway across the capacity range (1kW 1MW) 6000 Lifetime Cost ( ) 5500 Sensitivity of optimum system size to installed cost per kw Optimum (Minimum) Lifetime Cost of SOFC CHP system ( ) Optimum Generation Capacity of SOFC stack (kw) 4 Capacity (kw) 3 5000 200 400 600 800 1000 1200 1400 1600 0 SOFC base cost per kw installed ( /kw) 6 5 2 1 Cost-optimal size for residential applications is roughly 0.5 kwe, for capital cost of 800/kWe 20
DG generally has environmental benefits, but modelling helps reveal perverse effects Buyback Price vs CO2 Reduction for 1.1kW Stirling Engine (with 5kWh/h heat dump possible) CO2 Emission Avoided (kg) against Grid/Boiler Baseline 600 500 400 300 200 100 0 0 1 2 3 4 5 6 Buyback Price (p/kwh) 21 If heat can be wasted to exhaust by micro-chp, then it is often economically optimal to generate electricity to meet onsite loads and export to the grid, and to dump some of the heat generated. Wasted heat implies higher carbon emissions
Electricity Buyback (export) Prices 1500 Minimum Annualised cost ( ) 1450 0p/kWh 2p/kWh 4p/kWh 1400 1350 Current baseline cost 1300 22 1250 0 1 2 3 4 5 SOFC Stack Capacity (kwe)
Ramp Constraints SOFC Stack Capacity (kwe) 1.4 1.2 1 0.8 0.6 0.4 0.2 22 21.5 21 20.5 20 Boiler Capacity (kwth) Stack Cap Boiler Cap 0 0.002 0.01 0.05 0.1 0.2 0.3 0.4 1 Rate of Change of Current Density Limit (A/cm2/min) 19.5 23
Influence of thermal demands on micro-chp 8000 Case 1: Conventional Central Heating Space Heat Demand (kw) 6000 4000 2000 0 8000 5 10 15 20 Time (Hours) Case 4: 3kW Underfloor Heating System Space Heat Demand (kw) 24 6000 4000 2000 0 5 10 15 20 Time (Hours)
Conclusions Broadly, on DE Technology options are abundant, and improving System approach appropriate demand/supply, infrastructures, people, markets Active networks and DSM will be an important aspect in future distribution network and DG penetration scenarios. Plenty of barriers: technical, market, regulatory, Micro-CHP Economic and environmental benefit depending on Economics and environment aren t everything. Space, quality of service, etc Rough and tough technology may be better than highly optimised Interesting questions:- How do you quantify and model uncertainty in the new DE environment? Eg portfolios, real options Technical and economic questions about infrastructure transition 25
Publications A.D. Hawkes, P. Aguiar, C. A. Hernandez-Aramburo, M.A. Leach, N.P. Brandon, T.C. Green, C.S. Adjiman (2006) "Techno-Economic Modelling of a Solid Oxide Fuel Cell Stack for micro-chp". Journal of Power Sources. Vol 156/2 pp 321-333 Castillo-Castillo A and Leach M (2006). Technology Scales and Types in Future Urban Waste Strategies: Is Compliance Sustainable and Feasible? In proceedings of Waste 2006: Integrated Waste Management and Pollution Control Policy and Practice, Research and Solutions, The Waste Conference Ltd, Warwick. Hawkes A and Leach M (2005). Solid oxide fuel cell systems for residential microcombined heat and power in the UK: Key economic drivers. Journal of Power Sources 149 72-83. Hawkes A, Leach M, (2005). Impacts of temporal precision in optimisation modelling of micro-combined heat and power, Energy, Vol: 30, Pages: 1759 1779 Hawkes A and Leach M (2006). The Economic Value and Carbon Dioxide Emissions Implications of Community Heating Networks in the UK. 6th BIEE Academic Conference, St Johns College Oxford, September 20-21 2006. Submitted Hawkes AD and Leach MA (June 2006 accepted). Cost Effective Operating Strategy for Residential Micro Combined Heat and Power, Energy Hawkes A.D., Aguiar, P., Croxford, B., Leach, M.A., Adjiman, C.S., and Brandon, N.P. (September 2006 accepted ). Solid Oxide Fuel Cell Micro Combined Heat and Power System Operating Strategy: Options for Provision of Residential Space and Water Heating. Journal of Power Sources 26