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Integrated distributed energy evaluation software (IDEAS)Simulation of a micro-turbine based CHP system

S.M. Ameli *, B. Agnew, I. Potts

School of Mechanical and Systems Engineering, University of Newcastle upon Tyne, Newcastle NE1 7RU, UK

Received 24 February 2005; accepted 25 July 2005Available online 15 September 2005

Abstract

IDEAS was defined in University of Newcastle upon Tyne in United Kingdom as a joint academic-industry project, in order todevelop a comprehensive software package for designing, optimizing and monitoring of distributed energy systems based on micro-turbine, fuel cell and internal combustion engine driven systems using fossil fuels and renewables.

The IDEAS idea shaped in pursue of a series of actual projects at Research Centre for Innovation and Design (RCID) to suggestthe most energy consumption optimized and environmentally friendly distributed CHP system for some new residential complex aswell as some academic PhD thesis at Mechanical and Systems engineering department to optimize the performance of gas turbineand micro-turbine driven CHP system for generating power, cooling and heating.

Increasing number of CHP equipment suppliers and consultant engineering companies through UK and Europe and approvedinspiring short-term and long-term policies of EU for implementing the CHP systems, fascinating successful experiences in some EUcountries like Denmark in CHP implementation and lack of a comprehensive European based software package for designing andoptimizing of these systems, all supported the idea of developing the IDEAS.

IDEAS tends to be a complement to tens of small CHP systems related European software, each has been developed with limiteddata and a European version of similar powerful non-European (mostly American) software packages.

To gain an overview of the difficulties, musts, domain of the package abilities, required financial, human resources and informa-tion and also for a better presentation of the idea to absorb supports from both academic and industry possible partners, a micro-turbine driven CHP system was designed for a 71 dwelling residential complex in north of England.

This paper presents the works which have been done and yielded results about the requirements of developing IDEAS. 2005 Elsevier Ltd. All rights reserved.

Keywords: CHP; Combined heat power; Micro-turbine; IPS-Pro; Fuel cell; Renewable

1. Introduction

For an actual new residential complex including 71dwellings in north of England, simple daily electricity,hot water, and air conditioning load curves has beendeveloped at three different climate conditions of regionduring a year.

A CHP system uses one (and two) 60 kW CapstoneC60 micro-turbines was simulated using IPS-Pro

1359-4311/$ - see front matter 2005 Elsevier Ltd. All rights reserved.doi:10.1016/j.applthermaleng.2005.07.019

* Corresponding author. Tel.: +44 1670 859 525; fax: +44 1670 859529.

E-mail address:s.m.ameli@ncl.ac.uk(S.M. Ameli).

www.elsevier.com/locate/apthermeng

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thermal systems simulation software. With consideringdifferent operational situations and using the actualoperational data of used micro-turbines, utmost similar-ity with actual micro-turbine was achieved.

Different working schemes were considered based onusing one or two micro-turbine and following the elec-

tricity demand or working full load all times. For eachscheme, the related simulated design and related eco-nomic calculations were performed.

With using the actual energy tariffs and economicparameters, different schemes were compared andthe best one regarding shortest pay-back time waschosen.

1.1. CHP performance simulation

A CHP system driven by two 60 kW gas driven Cap-stone micro-turbines was designed for an actual residen-

tial complex in UK including 71 dwellings.Electricity and heat (hot water and air conditioning)

demand curves were developed using a simple HVACsoftware and some rough estimations on the type ofused building materials, number of occupants andother parameters but it was assured that the peakelectricity demand and total annual gas complywith the elementary estimations of proprietor (190 kWand 1 296 570 kW h/year comparing to 220 kW and1032290 kW h/year). The aim has been to develop anumerical model that simulates the actual case andmatches the proprietors estimation of peak consump-tion to use it as a comparison base for all parametricstudies.

Total Population assumed to be two hundred andfifty residents were. U values of materials, ventilationrate and other relevant parameters considered for a nor-mal energy efficient building.

Loads were calculated for every half an hour (thescheme that UK energy suppliers used to use for calcu-lating the bill) and the whole year was divided to threeparts (633 months) regarding to Weather conditionand based on simplified climate data of Newcastle uponTyne (1.37 W and 54.58 N longitude and latitude) forpast 10 years.

The whole system was simulated using thermal sys-tems simulation software (IPS-Pro) and available actualoperational data of Capstone 60 kW micro-turbine.Since the effectiveness of CHP systems closely dependsto usage of their generated heat, designed system wassupposed to meet the major part of heat demand insteadof electricity and the best simultaneous economical caseof using the system and grid was investigated. Twowater cycles for hot water and air conditioning wereconsidered and total piping length and pressure and heatloss along it was simulated in each cycle. Although all

Nomenclature

CHP combined heat and powerIDEAS integrated distributed energy evaluation soft-

ware

U overall heat transfer coefficientDp pressure differenceDgm variation of mechanical efficiency

Dge variation of electrical efficiencyDgs variation of isentropic efficiencyDhtc area variation of area of heat transfer

IPS-Pro process simulation program, a thermal sys-tems simulation software, http://www.sim-technology.com

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exact operational parameters of C60 micro-turbine wasnot available, extreme effort done to achieve utmostcompliance with present data.

Using an economic software and considering fourconditionsworking with one or two micro-turbineand all-time full load running or part-load operationto meet electricity demand,

Economic calculations were performed and the bestsystem and operational scheme was determined along

with detailed techno-economical calculations for everyhalf an hour during the year. For gas and electricity,the prices of just one supplier was considered, and it

was supposed that electricity selling price to the gridwould be the same as purchasing from the grid.

Micro-turbine lifetime set for 80000 h with 8000 hmaintenance cycle. Possible loans and its relevantparameters (loan interest rate. . .) were neglected.

Sensitivity studies for different parameters includingpower generation, part-load efficiency and heat demand

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were done to show the abilities and authenticity of sim-ulated system and to extract the necessary informationfor economic studies.

Following table shows the economic viability of eachof the considered operational scheme. Due to the largeamount of heat demand of this residential complex, asit is shown in following table, the best case (among thevery limited considered cases), would be running two60 kW micro-turbine full load all-time. If the extra heat(more than need for hot water and air conditioning),could be constantly used during the year for other fieldlike farming and so on, pay-back time would be

6.5 years that sounds very good for micro-turbine drivenCHP systems, otherwise it would be 10.5 years that isstill acceptable.

It should be noticed that utmost effort was done sothat this prototype reflects major aspects of the realIDEAS project which should be considered at different

development stages. No logic could be found on someassumptions (like the considered operational cases) interms of a real precise ready to set-up system for abovementioned residential complex.

2. Conclusions

During the process of developing the prototype inpast nine months, a clear idea about the requirementsand final shape and abilities of the software packagewas configured through many contacts with equipmentmanufacturers and suppliers, handling some powerfulrelevant software like IPS-Pro, Matlab and Flowmas-terwhich probably would play some important roles

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in the process of developing the intended software pack-age- and through working with and analysing some sim-ilar non-European packages to get familiar with theiradvantages and disadvantages.

Some of the foreseen characteristics of the packagewere introduced although it is believed and was dis-

cussed in detail that the comprehensiveness of the soft-ware package would be closely related to availableresources.

Novelty and singularity of the software package (withmentioned characteristics) in UK and Europe wasinvestigated.

Accuracy and comprehensiveness of proposed soft-ware package closely and equally depends to both col-lected information and effectiveness and compatibilityof the composed software and written algorithms.

Essential databases include but not limited to types,prices, operational characteristics and parameters andsuppliers of different micro/mini turbines, fuel cells

and internal combustion engines, popular building typesin UK and Europe with their architectural, mechanicalproperties, energy suppliers and energy tariffs, differentpipes and their properties, different heat exchangerswith their suppliers, prices and characteristics, fuel com-position for different regions and different suppliers,environmental laws for each region, loans, levy andother governmental regulations and laws for usingCHP systems in each region, all economic parametersincluding interest rates, inflation etc. for each region,weather data, building materials and climate conditionsfor each region, and so on.

Due to lack of some critical information at this stage,many assumptions were made to do this prototype. Typ-ical value and curves assumed for U, Dp of the pipes,Dgm, Dgeof the generator relating to load, Dgsof turbinerelating to mass flow, Dhtcand the area of heat exchang-ers relating to part load heat transfer.

Four typical operational schemes were supposed andall three major parts of simulation performed by existingsoftware neglecting their limitations and calculationmethod and assumptions.

It was verified that some major decisions should bemade at this first stage. Limitations and comprehensive-ness of the package both technically and geographicallyshould be definitely defined. Available resources shouldbe determined before starting the project. Each threemajor parts of the package (HVAC, technical and eco-nomical calculations) should be considered to be doneby existing software or by separate especially developed

ones. It is necessary that similar simulations and proto-types to be done for other considered hardware includ-ing fuel cell, internal combustion engine, absorptionsystems, renewable and so on before being able to definethe software limitations and requirements.

Singularity and novelty of the software very closely

relates to above mentioned parameters.Relations, recognition and suitable and wisely use ofthe data and experiences gathered in hundreds of rele-vant projects and software, will terribly reduce the vol-ume of necessary work and resources.

The core of the software or the computer logic shouldbe so precise and comprehensive that while makes thebest use of available data, could make the best rationalassumptions in case.

The major challenge would be making the softwarepackage as user friendly as possible while keeping it pre-cise and technically accurate.

Acknowledgements

The authors wish to thank Brian Dixon and PaulFisher in RCID for their kind cooperation and support,Capstone Co. for its inspiration and information.

Further reading

[1] I. Krepchin, Distributed Generation: A Tool for Power Reliabilityand Quality, London, FT Energy, 2000.

[2] H.L. Willis, W.G. Scott, Distributed Power Generation: Planningand Evaluation, Marcel Dekker, 2000.

[3] European Commission, Integration: integration of renewableenergy sources and distributed generation in energy supplysystems, Energy, Environment and sustainable Development,2001.

[4] G. Francesco, Distributed generation versus centralised supply: asocial cost-benefit analysis, Department of Applied Economics,University of Cambridge, 2003.

[5] N.A. Kheir, Systems Modelling and Computer Simulation,Marcel Dekker, New York, 1996.

[6] E.P. Grohnheit, Energy policy responses to the climate changechallenge: the consistency of European CHP, renewables andenergy efficiency policies, Forskningscenter Ris (1999).

[7] A. Scott Spiewak, Cogeneration and Small Power ProductionManual, Fairmont Press, Englewood Cliffs, Lilburn, GA, 1991.

[8] E.M. Smith, Thermal Design of Heat Exchangers: A NumericalApproachDirect Sizing and Stepwise Rating, John Wiley &Sons, 1996.

[9] S. Kakac, Heat Exchangers: Selection, Rating, and ThermalDesign, CRC Press, Boca Raton, 2002.

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