Performance Assessment of Self-aspirated LPG Cook- stoves with Porous Radiant Burner
3.3.1 Techno-economic Assessment (TEA) of medium scale PRB
The purchase price of various components has been obtained from the field/market survey. The assumptions made during the study are listed below:
1. The capital cost includes the transportation fee.
2. Maintenance cost include both burner head cost and maintenance fee.
3. The cost of LPG is based on the price provided by Indane Gas (Indian Oil).
From the capital cost of stoves, it is seen that PRB stove is cheaper with a unit capital cost of ₹700, than the conventional stove which costs around ₹1,150. This is due to lower manufacturing and burner cost of the PRB stove. The annual operating cost diagram (illustrated in Fig. 3.13) shows that the conventional stove demand higher annual operating cost of ₹2,15,498 than the PRB stove, which is just ₹1,76,014 for the same power input of 5 kW. It should be noted that the same functional unit has been considered for all power inputs and therefore, the annual operating cost of the conventional burner is the same for all power inputs. With increase in power input, annual operating cost difference between CB and PRB stoves increases. Since, at higher input power of 10 kW, thermal efficiency of conventional stove is very low (36%) as compared to PRB stove (52.6%). This results in increase in the annual operating cost saving of PRB stove from ₹39,484 to ₹68,240. Considering 10 year of service, the cost for owning and operating the stoves for medium scale cooking purpose has been estimated from the life cycle cost analysis.
It is clearly seen from Fig. 3.14 that share of capital cost in case of conventional stove is around 5%, whereas in case of PRB stove these are less than 0.5%, which means that around 99.5% of expense is in fuel consumption, due to which the energy efficient PRB stove is very cost effective.
Fig. 3.13: Annual operating cost diagram.
Fig. 3.14: Percentage cost share for cook-stoves.
To find the operating cost saving from the replacement of conventional stove by PRB stove in its life time, a graph illustrating the Annual operating cost saving over a period of 10 years for 5-10 kW input power is presented in Fig. 3.15. From Fig. 3.15, it is observed that the replacement of single PRB may save the operating cost of ₹3,94,136
to ₹6,81,695 for 5 to 10 kW input powers, respectively in the life span of 10 yr. The total annual expenditures of LPG stove with PRB, which includes capital cost, operating cost and emissions cost, are ₹1,87,333 for 5 kW input power and ₹1,56,612 for 10 kW input power and the yearly saving may rise from ₹42,157 to ₹72,915 for same power inputs.
Methods of financial appraisal explained in Section 3.3 have now been used to compare the cost parameters in relation to two different types of medium scale LPG cook-stove, i.e. optional case (PRB stove) with the original case (conventional stove).
Fig. 3.15: Cumulative annual saving of the PRB stove.
Table 3.9 shows the calculated value of the annual saving, the present worth of the annual saving and the cumulative present worth of the annual saving for each year of life of the PRB cook-stove at 5 kW input power. With 5% inflation rate and 8% interest rate, the cumulative present worth of the annual savings for PRB stove over the life has been found as ₹3,44,991. The investment for the PRB stove is ₹700. It means that by investing ₹700 to procure a cook-stove today, one can save ₹3,44,991 over the life of the stove. Fig. 3.16 shows PRB cook-stove’s NPV for 5-10 kW input power range. It is clear from Fig. 3.16 that with increasing input power NPV increases and largest NPV of ₹5,96,708 has been found at 10 kW input power.
Table 3.9: Economics of the medium scale cook-stove with PRB at 5 kW input power.
Year Annual
savings (₹)
Present worth of annual saving (₹)
Present worth of cumulative saving (₹)
1 42156.56 39033.85 39033.85
2 44264.39 37949.58 76983.43
3 46477.61 36895.43 113878.86
4 48801.49 35870.55 149749.41
5 51241.56 34874.15 184623.55
6 53803.64 33905.42 218528.98
7 56493.83 32963.61 251492.58
8 59318.52 32047.95 283540.53
9 62284.44 31157.73 314698.26
10 65398.66 30292.24 344990.49
Internal Rate of Return (IRR) is a financial ratio, used to calculate the yearly return generated from the proposed investment. According to this method, the rate of return is worked out by arriving at the percentage ratio of the net gain over the initial anticipated investment of the project. The IRR of PRB stove has a high value of 5573.5% and 9642.2% for 5 and 10 kW respectively, as the initial investment for one PRB stove was only ₹700 and the calculated average total annual cost saving are ₹42,157 and ₹72,915 for 5 and 10 kW, respectively. At 5 kW with an IRR of 5573.5%, the PRB technology is expected to earn ₹56 out of each ₹1 invested (yearly) and maximum of ₹96 at 10 kW with an IRR of 9642.2%. The payback period of less than a week for all input power shows recoupment of the original capital invested. Based on the functional unit selected for this study, the maximum and minimum time duration for PRB stove to overcome initial investment are estimated to be only 6 and 4 days at 5 kW and 10 kW power inputs, respectively. This short duration of payback period is possible as the daily savings are ₹115 and ₹200 for mentioned input power and cost of PRB stove is only
₹700.
Fig. 3.16: Net present value (NPV) for 5-10 kW medium scale PRB cook-stove.