OPTIMUM SIZING OF A STAND-ALONE WIND-DIESEL SYSTEM ON THE BASIS OF LIFE CYCLE COST ANALYSIS Kaldellis J.K., Kavadias K.A. Lab of Soft Energy Applications & Environmental Protection, Mechanical Eng. Dept, TEI of Piraeus P.O. Box 41046, Athens 12201, GREECE Tel , FAX

INTRODUCTION (1/2) Almost two billion people have no direct access to electrical networks, 500,000 of them living in European Union and more than one tenth of them in Greece. An autonomous wind-diesel system is one of the most interesting and environmental friendly technological solutions for the electrification of remote consumers or even entire rural areas. The primary objective of this current study is to determine the optimum dimensions of an appropriate stand alone wind-diesel system, able to cover the energy demand of remote consumers, using long-term measurements, under the restriction of minimum life-cycle cost. In most previously published works the system configuration selection was based on a minimum first installation cost analysis only. J.K. Kaldellis, K.A. Kavadias (Lab of Soft Energy Applications & Environmental Protection)

INTRODUCTION (2/2) For this purpose an integrated cost-benefit model is developed from first principles, able to estimate the financial behaviour of similar applications on a long-term operational schedule. In the proposed algorithm, besides the first installation cost, one takes into account the fixed and variable M&O cost, including fuel escalation and local market inflation rate. Using the proposed analysis one may prove that wind-based stand- alone systems, including a properly sized battery, lead to significant reduction of the fuel consumption in comparison with a diesel-only installation, also protecting the diesel generator from increased wear. Special emphasis is put on investigating the impact of the operational (service) period of the installation on the corresponding energy production cost. J.K. Kaldellis, K.A. Kavadias (Lab of Soft Energy Applications & Environmental Protection)

PROPOSED SOLUTION (1/5) J.K. Kaldellis, K.A. Kavadias (Lab of Soft Energy Applications & Environmental Protection)

During the system operation, the following energy production scenarios exist: Energy (AC current) is produced by the micro wind converter and sent directly to the consumption Energy is produced (AC current) by the small diesel-electric generator and is forwarded to the consumption The energy output of the wind turbine (not absorbed by the consumption-energy surplus) is stored at the batteries via the charge controller The battery is used to cover the energy deficit via the DC/AC inverter PROPOSED SOLUTION (2/5) J.K. Kaldellis, K.A. Kavadias (Lab of Soft Energy Applications & Environmental Protection)

 This system should be capable of facing a remote consumer’s electricity demand (e.g. a four to six member family), with rational long- term operational cost.  The specific remote consumer investigated is basically a rural household profile (not an average load taken from typical users).  The annual peak load does not exceed 3.5kW, while the annual energy consumption is around 4750kWh. PROPOSED SOLUTION (3/5) J.K. Kaldellis, K.A. Kavadias (Lab of Soft Energy Applications & Environmental Protection)

The governing parameters that should be defined are:  the rated power of the wind turbine  the battery maximum capacity  the annual diesel-oil consumption The new numerical code is used to carry out the necessary parametrical analysis on an hourly energy production-demand basis, targeting to estimate the wind turbine’s rated power and the battery capacity, given the annual permitted oil consumption. Emphasis is laid on obtaining zero-load rejection operation PROPOSED SOLUTION (4/5) J.K. Kaldellis, K.A. Kavadias (Lab of Soft Energy Applications & Environmental Protection)

Given the "M f " value and for each "N o " and "Q max " pair, the "WIND- DIESEL I" algorithm is executed for all the time-period selected (e.g. one month or even three years). The appropriate (M f, N o, Q max ) combinations guarantees the stand- alone system energy autonomy. PROPOSED SOLUTION (5/5) J.K. Kaldellis, K.A. Kavadias (Lab of Soft Energy Applications & Environmental Protection)

LIFE CYCLE COST MODEL (1/4) The present value of the entire investment cost of a stand-alone wind- diesel power system during its life cycle is a combination of the initial installation cost and the corresponding maintenance and operation cost. First Installation Cost The initial investment cost includes the market (ex-works) price of the installation components (i.e. wind turbine, battery, diesel generator and electronic devices, including inverter, UPS, rectifier and charge controller cost) and the corresponding balance of the plant cost. J.K. Kaldellis, K.A. Kavadias (Lab of Soft Energy Applications & Environmental Protection)

Fixed Maintenance and Operation Cost In the present analysis, the fixed M&O cost also considers the fuel cost consumed by the diesel-electric generator. The annual fixed M&O cost "FC WT “ can be expressed as a fraction "m" of the initial capital invested, furthermore including an annual inflation rate "g m " The fuel consumption cost "FC D " results by the annual diesel-oil quantity consumed "M f ", the current fuel price "c o " and the oil price escalation rate "e" LIFE CYCLE COST MODEL (2/4) J.K. Kaldellis, K.A. Kavadias (Lab of Soft Energy Applications & Environmental Protection)

Variable maintenance and operation cost It depends on the replacement of "k o " major parts of the installation, which have a shorter lifetime "n k " than the complete installation. In the present analysis one takes into account the diesel-electric generator and the battery bank replacement. while "h d " and "h b " describe the purchase cost mean annual change combined with the corresponding technological improvement rate LIFE CYCLE COST MODEL (3/4) J.K. Kaldellis, K.A. Kavadias (Lab of Soft Energy Applications & Environmental Protection)

Life Cycle Energy Production Cost The energy production cost is given by dividing the present value of the installation total cost with the corresponding electricity production. The energy production cost of the installation strongly depends on the service period "n" of the installation, i.e.: The current electricity production cost "c e ", after n-years of operation: The proposed model includes the diesel-only solution (i.e. IC o =φ.N d, N o =0, r b =0, M f =M max ) as well as the zero-diesel configuration (i.e. IC d =0, r d =0, M f =0) LIFE CYCLE COST MODEL (4/4) J.K. Kaldellis, K.A. Kavadias (Lab of Soft Energy Applications & Environmental Protection)

ANALYSIS OF THE PARAMETERS INVOLVED The main parameters involved in the electricity production cost procedure are:  The local market capital cost (x,y,z)  The M&O inflation rate (x)  The oil price annual escalation rate (y)  The electricity price annual escalation rate (z) J.K. Kaldellis, K.A. Kavadias (Lab of Soft Energy Applications & Environmental Protection)

APPLICATIONS RESULTS (1/5) The proposed analysis is being applied to typical remote consumers located in a small island of N. Aegean Sea. The island of Skiros is a small island of NW Aegean Sea, belonging to the Sporades complex. J.K. Kaldellis, K.A. Kavadias (Lab of Soft Energy Applications & Environmental Protection)

The island has a medium-strong wind potential, taking into consideration that the annual mean wind speed approaches the 6.8m/s at 10m height. APPLICATIONS RESULTS (2/5) J.K. Kaldellis, K.A. Kavadias (Lab of Soft Energy Applications & Environmental Protection)

 For a low (M f =100kg/y) and a high (M f =500kg/y) annual diesel oil contribution cases, one may observe that there is a remarkable electricity cost decrease with the increase of the installation service period. APPLICATIONS RESULTS (3/5) J.K. Kaldellis, K.A. Kavadias (Lab of Soft Energy Applications & Environmental Protection)

APPLICATIONS RESULTS (4/5)  For zero (wind only) or low diesel-oil contribution cases there is a considerable cost decrease between (5) and (10) years and between (15) and (20) years  The cost decrease between (10) and (15) years is quite small, due to the increase of the variable M&O cost contribution J.K. Kaldellis, K.A. Kavadias (Lab of Soft Energy Applications & Environmental Protection)

 In all cases examined, the optimum life cycle electricity production cost of the wind- diesel system investigated is slightly above 0.6€/kWh APPLICATIONS RESULTS (5/5)  The minimum electricity production cost is remarkably decreased between the 5 th and the 10 th year of operation of the system, being accordingly almost constant  There is a significant optimum annual oil consumption decrease (≈300kg/yr) when the service period of the hybrid station increases from 5 to 20 years J.K. Kaldellis, K.A. Kavadias (Lab of Soft Energy Applications & Environmental Protection)

CONCLUSIONS (1/2) An integrated cost-benefit model is developed from first principles, able to estimate the financial behaviour of an energy autonomous hybrid wind-diesel-battery system on a long-term operational schedule. For this purpose one should first define the optimum dimensions of the proposed system, able to cover the energy demand of remote consumers, under the restriction of minimum life-cycle cost. The main parameters to be predicted are the wind turbine rated power, the corresponding battery capacity and the annual oil consumption required in order to guarantee energy autonomy of the entire stand-alone installation. Accordingly, a total electricity production cost calculation model is developed, taking explicitly into consideration the desired service period of the complete installation. J.K. Kaldellis, K.A. Kavadias (Lab of Soft Energy Applications & Environmental Protection)

CONCLUSIONS (2/2) Finally, the application of the complete analysis on a selected typical island region indicates that the proposed hybrid system is a reliable and a cost effective solution for the electrification of numerous isolated consumers. According to the results obtained, one should point out the remarkable diesel-oil consumption decrease as the desired service period of the hybrid station increases, in order to minimize the corresponding life cycle electricity production cost. In any case, the estimated long-term electricity production cost of the proposed hybrid system is considerably lower than the current operational cost of several existing small autonomous thermal power stations throughout Aegean Archipelago. Recapitulating, one may definitely state that a properly sized stand-alone wind-diesel system is a motivating prospect for the energy demand problems of numerous existing isolated consumers all around Europe. J.K. Kaldellis, K.A. Kavadias (Lab of Soft Energy Applications & Environmental Protection)