Biomass energy cost and feasibility of gasifier based biomass power generation system

Headnote

Abstract: The present research work has been carried out on biomass based on 10 kW capacity gasifier power generation system installed at College of Agricultural Engineering and Technology, Dr. Panjabrao Deshmukh Agricultural University (Dr. PDKV), Akola Maharashtra, India. The main objectives were to evaluate various costs and benefits involved in the power generation system. The costs of energy per unit were calculated for the first year of operation. The economics of gasifier based power generation system and thereby the feasibility of the system was examined by estimating per unit cost, Net Present Value (NPV), Benefit Cost Ratio (BCR), Internal Rate of Return (IRR) and payback period. The discount cash flow method was used to find out the IRR. In the present analysis, three costs viz., installed capital cost, operation and maintenance cost, and levelised replacement cost were examined for the evaluation of the power generation per unit. Discount rate on investment in case of subsidy (Case I) and in case without subsidy (Case II) for installation cost of system was considered as 12.75%. The BCR comes in Case I for operating duration of 22 h, 20 h, and 16 h are 1.24, 1.18, and 1.13, respectively. Similarly for Case II BCR comes 1.44, 1.38, and 2.39. The IRR comes in Case I for operating duration of 22 h, 20 h, and 16 h are 26%, 22%, and 19%, respectively. Similarly for Case II, IRR comes 52%, 44%, and 39% for operating duration of 22 h, 20 h, and 16 h, respectively. The payback period in the present analysis was worked out. The payback period for biomass based gasifier power generation system was observed to be for Case I from three to four years and for Case II it was one to two years.

Keywords: cost of biomass energy, biomass power generation system discounted cash flow, benefit cost ratio, net present value, payback period, internal rate of return

DOI: 10.3965/j.ijabe.20130604.007

(ProQuest: ... denotes formulae omitted.)

1 Introduction

India is a rural based country and nearly about 65% populace is living in villages. Farming is the basic source for earning which requires energy as an intensive measure for production. The country itself faces acute shortages of electricity, which affects the irrigation facility in the villages across the country. The low level of increasing power plants, improper prediction of energy requirement and depletion of fossils fuel has restricted to supply of adequate power to farming. To avoid the circumstances of the power, another way is use of the renewable energy sources. The villages in the country are naturally endowed with variety of natural energy sources, by which means it is possible to develop self energy generating villages to satisfy the energy demand. The villages in the country have strong and abundant natural energy sources. The biomass in villages is available in variety of forms. The crop residue and livestock waste and the forest excess wood are main available sources of biomass in the villages. India is emerging as one of the fastest growing countries in the world with a GDP growth consistently exceeding 8% for the past couple of years and this trend is expected to continue. Energy being the driver of this growth, its availability is of the utmost importance to sustain this level of growth. The official projections show that the energy demand is expected to be more than three to four times the current level in another 25 years[1]. Though 74% of Indian villages were electrified as of March 2005[2] only 54.9% of households had access to electricity13,41. About 42% of people had access to clean LPG for cooking as of January 2005. With respect to the rural-urban divide, in 2005, 9% of rural households had access to LPG whereas about 57% of urban households had access[4,5]. Biomass of agro residue, cattle waste was given considerable importance as biofuels at domestic cooking, industrial application and some of extent power generation for satisfying the energy demands of the end users[6]. Biomass energy sources may be able to offer socio-economical and technical benefits compared to other renewable energy sources. The exact predication of the socio-economic benefit has not yet been completed in India and could help to guide level of additional subsidies that may be appropriate for bioenergy compared to the other renewable energy sources171. Biomass source is the emerging energy among renewable energy sources having potential to fulfill the energy demand of the rural areas to enhance the rural economy in developing countries.

The present research was mainly intended towards the assessment cost of energy generation and the feasibility for the power generation through biomass based gasifier power generation system. This information will help in deciding in retrofitting such system in rural area of the country to fulfill the energy demand. The gasifier based power generation system installed at Dr. Panjabrao Deshmukh Agricultural University (Dr. PDKV), Akola was studied as a case for the research project work considering the various aspects of energy generation with the various cost measures.

2 Materials and methods

The present study was carried out at biomass power generation system of 10 kW installed capacity at the College of Agricultural Engineering and Technology, Dr. PDKV, Akola Maharashtra, India. The system has been installed during March, 2009. The installation and the maintenance cost of the system for turnkey operation was gathered and determined. In the present study, cost of energy generation has been evaluated. The cost of energy generation was evaluated by considering the optimum performance of the gasifier system[8"10]. The life cycle cost of energy generation was determined by considering the present economic appraisal. The feasibility of the power generation of gasifier system was evaluated by discounted cash flow technique (DCF)[8"10]. The parameters like net present value, benefit-cost ratio, internal rate of return and payback period of the system was evaluated by considering the current nature of discount rate.

2.1 Theory of economic analysis

The economics of gasifier based power generation system was calculated by evaluating various costs measured and by using the discounted cash flow techniques for system economic feasibility. The data regarding installation cost, cost of fuel and cost of labour for the case determined by operations considered.

The present analysis has been carried out for power generation of 22 h, 20 h, 16 h with the scenario of without subsidy (Case I) and subsidy of 50 percent (Case II) on total installation cost of gasifier based power generation system.

2.1.1 Cost of energy generation

The cost of energy generation from biomass based gasifier system has decreased significantly over the past decades. Three methods are customarily used to measure the costs and economic performance of power generation system. This begins with the installed capital cost (ICC), specific capital cost and cost of energy18"101.

(1) Installed capital cost

This measure of cost includes all planning, equipment purchase, construction and installation costs for a turnkey of biomass based gasifier power generation system, ready to operate. As such, this cost includes installation at the site together with all maintenance and other supporting infrastructure170,111.

(2) System specific capital cost

This measure of the cost combines installed cost and the power generation per year. The capital cost is the installed cost to obtain energy generation per year.

...(1)

This capital cost does not include the cost of operation and maintenance over the lifetime of the system.

(3) Cost of energy generation

This cost is the most comprehensive measure of power generation system, which is the cost of energy (CoE). This measure incorporates all elements of cost, i.e. installed capital cost, cost of operation and maintenance, cost of major overhauls and subsystem replacement.

...(2)

where, ICC, installed capital cost; FCR, annual fixed charge rate; O&M, operation and maintenance cost; LRC, levelised replacement cost (considered 25% over O&M).

2.2 Economic feasibility of biomass power system

The project evaluation technique (discounted cash flow) was used to measure the economic feasibility of power generation system. This technique measures the productivity of the capital invested and for which the flow of costs and returns over life period (project life = 20 years). These costs can be brought to refer to the particular point of time i. e., present period by discounting them[11"13].

Comparative picture of different measures of capital productivity used in economic evaluation of investment in biomass energy systems used are: net present value, benefit cost ratio, internal rate of return and payback period. 2.2.1 Net present value (NPV)

In this method, generally the discounted rate/ compound rate, which reflects the price of the investment funds, is used to arrive at costs and returns to a common point of time. These costs are subtracted from the return to obtain the net present values of the systems. The positive net present values indicate that the investment is worthwhile and the size of the NPV indicates how worthwhile the project is in utilizing the resources to maximize income. Following expression is used to work out the net present value:

...(3)

where, R is the returns in the year t; C is the costs in year t, N is the project life; i is the discount rate in per cent.

The decision criteria are: If NPV > 0, Investment is worthwhile; NPV < 0, Investment is not worthwhile; if NPV = 0, Neutral case.

2.2.2 Benefit cost ratio (BCR)

The benefit cost ratio measures the returns or benefit per unit of cost of investment.

...(4)

The decision criteria are: if BCR > 1, Investment is worthwhile; if BCR < 1, Investment is not worthwhile; if BCR = 1, Neutral case.

2.2.3 Internal rate of return (IRR)

The internal rate of return means the discounted/ compound rate at which the present value of returns equals that of costs. Accordingly the derived discounted rate (IRR) is compared with the price of the investment funds to know the worthiness of the project.

...(5)

The decision profitability criteria are: if IRR > 1, Investment is worthwhile; if IRR < 1, Investment is not worthwhile; if IRR = 1, Neutral case.

2.2.4 Payback period

This is the simplest of the techniques for evaluating an investment proposal. It is defined as the time period within which the initial investment of the project is recovered in the form of benefits. In other words, this is the length of time between the starting time of the project and the time when the initial investment is recoupled in the form of yearly benefits. Expressing it in notation:

...(6)

where, P is the payback period; I is the initial investment, and C is the yearly net cash flow.

3 Results and discussion

3.1 Economic analysis of power generation system

The economics of biomass based power generation system and feasibility by estimating per unit cost in initial year and by estimation of NPV, BCR, IRR and payback period. The information gathered regarding capital cost and energy generation for the one year are indicated in Table 1. The present analysis has been carried out for power generation of 22 h, 20 h, 16 h with the scenario of without subsidy (Case I) and subsidy of 50% (Case II) on total installation cost of gasifier based power generation system. The maintenance cost was considered for both scenarios of one per cent to the installed cost. Similarly, levelised replacement cost was considered 25% of maintenance cost. The gasifier based power generation system is operated to 22 h, 20 h, and 16 h having biomass fuel feeding of 15 kg/h. The cost of purchased biomass fuel (raw material) was 1.5 INR/kg. The gasifier system has been considered for 300 days in operation in one year. For the condition of 22 h, 20 h, and 16 h, three labours were required to operate the power generation system. The cost per man laborers per day was INR 80. While considering the above stated fact the operational requirement of fuel and labour with maintenance cost, the capital statement and energy production scenario is depicted in Table 1.

The total installation cost for a 10 kW capacity gasifier based power generation system comes to INR 650 000 in case I and INR 325 000 in case II. The annual energy generation is 66 000 kWh for 22 h, 60 000 kWh for 20 h and 48 000 kWh for 16 h in case I and case II. The cost of electricity for calculating the grass annual income from the power generation system were considered as 6 INR/kWh as per present tariff of Maharashtra Electricity Regulation Board for biomass energy generation system. The FCR of power generation system was INR 12.75% for both cases. The interest rate for biomass based power generation system is reported to be 13%[14]. The project life time of gasifier based power generation system was considered for 20 year. The gross annual income was obtained INR 396 000 for 22 h, INR 360 000 for 20 h and INR 288 000 for 16 h in both cases. The annual operation and maintenance cost in both cases was INR 228 625 for 22 h, INR 215 125 for 20 h and INR 164 125 for 16 h. The return per unit of energy generation was obtained in case I of 1.261 INR/kWh for 22 h, 1.01 INR/kWh for 20 h and 0.831 INR/kWh for 16 h. In case II, return per unit of energy generation was obtained 1.887 INR/kWh for 22 h, 1.698 INR/kWh for 20 h and 1.685 for 16 h. The economic return of 0.3 millions USD/year is reported[14]. The reported electricity revenue of biomass based project is about 10.34 euro/GJ[16] Levelised replacement cost was considered to be 25% on maintenance cost.

3.1.1 Cost of energy generation (Case I)

The annual energy generation for operating of 22 h, 20 h, and 16 h was 66 000 kWh, 60 000 kWh and 48 000 kWh respectively. The ICC (all equipment) at value of in case I of INR 650 000 for 10 kW power generation installed capacity. The system specific capital cost of biomass power generation system was calculated for Case I of 22 h, 20 h and 16 h comes to be 9.84, 10.83 and 13.54 INR (kWh/yr), respectively. Capital cost component was calculated using these specific capital cost and FCR of 12.75 per cent which comes to be 1.25, 1.38 and 1.72 INR/kWh for 22 h, 20 h and 16 h respectively. The interest rate for 50 kWe biomass project is reported as 13% and 10% for the useful life of 20 years[14,17]. Annual operation and maintenance was INR 228625, INR 215125 and INR 164125 for biomass based power generation system and these were 3. 46, 3.59 and 3.42 INR/kWh for 22 h, 20 h and 16 h, respectively. The operating cost was reported for biomass project of 4% to the total installation cost[16]. The cost of levelised replacement were examined by considering 25 per cent of operation and maintenance cost of biomass based gasifier power system, which comes to be 0.0246, 0.0270 and 0.0338 INR/kWh. The potential and cost of energy of biomass have reported by Downing & Robin 1996[18]. The case study of biomass based power generation is reported by Ravindranath, 2004[19].

The cost of energy for the biomass based gasifier power generation system is the equal to sum of three component mentioned above, i.e., capital cost component (1.25, 1.38, 1.72 INR/kWh), operation and maintenance cost (3.46, 3.59, 3.42 INR/kWh) and cost of replacement (0.0246, 0.0270, 0.0338 INR/kWh) giving a total of 4.74, 4.10 and 5.10 INR/kWh for 22 h, 20 h and 16 h operation of power generation system respectively. The costs of electricity generation from biomass based project are reported as 0.0 USD/kWh[15], for rice hull as fuel 0.27 Yuan RMB/kWhp0]. The relative effect of these estimated cost values (Tables 2-4) gives insight into where the overall economics of the system may be impacted. From Tables 2-4, it is seen that the leading component of cost of bioenergy are of operation and maintenance cost followed by the cost of capital. The operation and maintenance cost in Case I represents 73%, 72% and 62% for 22 h, 20 h and 16 h operation of power generation system respectively. The operation and maintenance cost for 10% wood co-firing biomass project is reported to be 0.04 p/kWh at which fuel cost is found about 0.16 p/kWh[22]. The replacement cost of the system is in the range of not more than 0.65% for 22 h, 20 h and 16 h operation of power generation system respectively.

3.1.2 Profit statement of biomass power system (Case I)

The system benefit for the overall project has been determined over a year for operation of 22 h, 20 h, and 16 h. The information presented Table 5 shows the profit statement for 10 kW gasifier based power generation system for one year. The profit per unit was worked out to be 1.268 INR/kWh for 22 h, 1.008 INR/kWh for 20 h and 0.822 INR/kWh for 16 h. The gross annual income has been calculated by considering annual energy production and the return on per unit of energy generation. The gross annual income comes to INR 396 000, INR 360 000 and INR 280 000 and the production cost of energy comes to be (INR 4.74x66 000) INR 312 842, (INR 4.99x60 000) INR 294 400 and (INR 5.178x48 000) INR 248 544 giving a profit for the first year of operation (22 h, 20 h and 16 h operating duration per day) as INR 83 688, INR 60 480, INR 39 455. The reported income from selling of electricity from biomass project is 1.66 baht/year[23].

3.1.3 Cost of energy generation (Case II)

The annual energy generation for operating of 22 h, 20 h, and 16 h was 66 000 kWh, 60 000 kWh and 48 000 kWh, respectively. The ICC (all equipment) at value of INR 325000 for 10 kW power generation installed capacity (case II). The similar case was considered at 40% subsidy of total cost of project[24]. The specific capital cost of biomass power generation system was calculated for case II of 22 h, 20 h and 16 h which comes to be 4.92, 5.41 and 6.77 INR/kWh per year, respectively. Capital cost component were calculated using these specific capital cost and FCR of 12.75 per cent which comes to be 0.63, 0.69 and 0.86 INR/kWh for 22 h, 20 h and 16 h respectively. The capital cost for the biomass system has been reported as 1 588, 1 696, 1 371, 1 108 and 1 350 $/kW[25]. The ICC for wood fired system is reported as $1765/kWe[26]. Besterbroer et al., have reported capital cost of biomass project in range of $5 835-$8 335 per kWe[27]. Annual operation and maintenance was INR 228625, INR 215125 and INR 164125 for biomass based power generation system and these were 3.46, 3.59 and 3.42 INR/kWh for 22 h, 20 h and 16 h, respectively. The cost of levelised replacement was examined by considering 25% of operation and maintenance cost of biomass based gasifier power system, which comes to be 0.0246, 0.0270 and 0.0338 INR/kWh.

The cost of energy for the biomass based gasifier power generation system is equal to the sum of three components mentioned above, i.e., capital cost component (0.63, 0.69 and 0.86 INR/kWh), operation and maintenance cost (3.46, 3.59, 3.42 INR/kWh) and cost of replacement (0.0246, 0.0270, 0.0338 INR/kWh) giving a total of 4.11, 4.30 and 4.31 INR/kWh for 22 h, 20 h and 16 h operation of power generation system respectively. The reported cost of electricity generation from biomass for pyrolysis and combustion are 9.40 c/kWh and 10.79 c/kWh respectively^7] and 3.50 $c/kWh for biomass project[21]. The cost of biomass energy for the scenario considered was reported to be Rs. 68, Rs. 51 and Rs. 47 per GJ[28]. The specific capital cost was assessed to be £ 1035/kWe[29]. The relative effect of these estimated cost values (Tables 6-8) gives insight into where the overall economics of the system may be impacted. From Tables 6-8, it is seen that the leading component of cost of bioenergy are of operation and maintenance cost followed by the cost of capital. The reported capital per kWh of electricity generation from biomass is 0.28 p/kWh[22]. The operation and maintenance cost in case II represent 84%, 83% and 79% for 22 h, 20 h and 16 h operation of power generation system respectively. The estimated maintenance cost per annum was 1.2% of the total investment of 0.60 $c/kWh[21]. The replacement cost of the system is in the range not more than 0.77% for 22 h, 20 h and 16 h operation of power generation system respectively.

3.1.4 Profit statement of biomass power system (Case II)

The system benefit for the overall project has been determined over a year for operation of 22 h, 20 h, and 16 h. The information presented Table 9 shows the profit statement for 10 kW gasifier based power generation system for one year having considering 50 per cent financial assistance (subsidy). The profit per unit was worked out to be 1.881 INR/kWh for 22 h, 1.698 INR/kWh for 20 h and 1.685 INR/kWh for 16 h. The gross annual income has been calculated by considering annual energy production and the return on per unit of energy generation. The gross annual income comes to INR 396 000, INR 360 000 and INR 280 000 and the production cost of energy comes to be (INR 4.11x66 000) INR 271 260, (INR 4.30x60 000) INR 258 000 and (INR 4.31x48 000) INR 206880 giving a profit for the first year of operation (22 h, 20 h and 16 h operating duration per day) as INR 124146, INR 101 880, INR 80 880. The electricity revenue per kWh is reported as 0.037 euro[16].

3.2 Economic feasibility of biomass power generation system

For initial project appraisal, some form of discount cash flow (DCF) is normally required. In economic terms, the discount rate is an indication of the opportunity cost of capital to owner. This cost is the return on the next base investment and if the rate is below it, then it is not worthwhile to invest in the system. In India, at present discount rate of gasifier based power generation system in industrial sector was 12.75% which would for commercial power generation system reflect the value placed on capital and the perceived level of risks[9'10'14'22'24].

For the cost and the return from biomass power generation system in the above analysis for first year of installation, the time factor was considered. To bring the past and future costs to present, worth corresponding and discounting technique was used with a 12.75% discount rate. The economic feasibility of gasifier based power generation system was examined by working out the NPV, BCR, IRR, payback period, using operation and maintenance cost for both the cases with gross annual income from the system in one year. For the income calculations, the return per unit was calculated which has been taken as income generation of the system in the project life time (20 years).

The cost of replacement was considered as 25% on the total maintenance cost of the system. The present worth of benefits used at 12.75% discount rate for case I give INR 2 824 138, INR 2 567 398, and INR 2 053 919 and for case II give INR 2 824 138, INR 2 567 398 and INR 2 131 132. The present worth of cost used at 12.75% discount rate for case I give INR 2 280 476, INR 2 184 199, and INR 1 820 484 and for case II give INR 1 955 476, INR 1 859 199 and INR 889 486.

3.2.1 Net present value (NPV)

The Net present value was found to be positive in both cases. Hence it seems that the project is feasible and can be considered for the next parameters determination. The net present value was found to be INR 266 058 for 16 h, INR 412 353 for 20 h and INR 587 741 for 22 h in case I. The NPV for case II was INR 559700 for 16 h, INR 746353 for 20 h and INR 912741 for 22 h. The reported NPV 196960274 Dra at 40% subsidy[24].

3.2.2 Internal rate of return (IRR)

The IRR was found to be positive in both cases. The IRR was found to be 19% for 16 h, 22% for 20 h and 26% for 22 h in case I. For the case with subsidy (case II) IRR was 39% for 16 h, 44% for 20 h and 52% for 22 h. The reported IRR values for biomass project are 44.644 to 44.525% respectively1241, 30%[23], 19%[30] and 51%[31]. 3.2.3 Benefit cost ratio (BCR)

The information presented in Table 10 reveals that the benefit cost ratio was positive. The benefit cost ratios were found to be 1.13 for 16 h, 1.18 for 20 h and 1.24 for 22 h for without subsidy case. For the case with subsidy benefit cost ratios were observed to be 2.39 for 16 h, 1.38 for 20 h and 1.44 for 22 h. The reported benefit cost ratios for biomass based electricity generation projects are 2.270 to 2.763[24] and 1.68[30].

3.2.4 Payback period

The information presented in Table 10 reveals that the payback period was found to be in the range of four years to one year for case I and two years to one year for case II. The discounted payback period reported including subsidy (40%) is 2.905-2.914 years. The assessed payback periods are reported 7 years[30] and 2.28 years[31].

4 Conclusions

Biomass power generation cost was determined in term of INR/kWh. A simple technique was used in finding the cost of energy generation from biomass. The costs of biomass energy include the three costs namely installation cost, specific capital cost and the cost of energy generation. In cost of energy generation from the biomass sources, operation and maintenance cost is the leading cost component, then the installation cost. For both the cases operation and maintenance costs were observed in the range of 66%-73% (Case I) and 79%-84% (case II) in energy generation. The costs of energy generation varied with the burden of capital taking in to consideration for analysis. The cost of energy generation was observed to be less in case II as compared to case I which similarly affected on the profit of the system.

The economic feasibility of the biomass power generation system was determined over the life of the system. The results obtained from this method indicate that the implementation of the system is feasible for both cases with an acceptable NPV. The IRR in both cases were more than the discount rate considered for the system. The payback period of the power generation system for case I was in the range of first one to four years of operation and for case II was in the range of one to two years of operation. The benefit cost ratio was found out to be 2.39 jby considering present worth of cost and present worth of benefit which is more in case II for operating condition of 16 hours.

Sidebar

Citation: Khambalkar V P, Kankal U S, Karale D S, Gangde C N. Biomass energy cost and feasibility of gasifier based biomass power generation system. Int J Agrie & Biol Eng, 2013; 6(4): 55 - 63.

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