The extra space thus obtained on the roof is being utilised by two cabins, one canteen area with 10 tables and a capacity for seating about 60 people, a corner for the Inverter + Battery System and a showroom to showcase the company products.
Picking the Type of Solar system:
- Grid Tie System: A grid tie system is one in which the inverter output synchronises with the grid connection and feeds directly to the load without any storage medium in between. It is cheaper than hybrid and smaller in size as well. But the major problem in this is that it will not produce electricity when the grid is absent, even when the sun is shining merrily, due to anti islanding of the system. This meant that our Diesel consumption would not go down even by one bit. A turn around to the problem was that the DG will be switched ON and the inverter output would synchronise to the DG output when the power is down. But the deal breaker condition is that :
#1 you are not saving any diesel
#2 as the inverter output is supplying most of the load and the DG set we had would therefore run at a capacity of less than 30%, it would result in a carbon and soot build up inside the DG SET mechanism causing it run much inefficiently and reduce its life period.
#3 Also switching ON the DG set would require a couple minutes and even that would interrupt our sensitive server loads plus the LOSS in productivity.
- Off Grid System:
Simpler of the three systems, it uses Solar to serve the primary loads and charge the battery when PV is present while Grid is used to supply rest of the loads. When solar is down, then grid takes command over the entire load as well as the charging of the battery system. In case The grid is down then Battery + Solar supplies the load and if the PV is down as well then the responsibility shifts to the battery alone.This is a simple enough system that most of us are familiar with due to its availability for long. But a major drawback of the system is that it is not the best system for the battery life and batteries are AFTER ALL the most expensive components of the entire system.
Thus the off grid system was discarded (although one unit of 6kVA still functions as a UPS to the server)
- Hybrid System:
Thus comparing the features of the above two systems with those mentioned above for Hybrid systems we felt that for our case, even though the other two have their own benefits, the Hybrid system would be the most suitable and more beneficial in terms of utility and a faster payback period.
- Initial Investment:
PV Panels: 250×120= 30KW= 11,42,400
Inverter: 100kVA= 9,23,950
Batteries: 2Vx120 /300Ah = 5,83,000
Mounting structure= 73,200
Installation and commissioning= 60000
- Savings & Payback Period =
Per unit cost of electricity= 9.86
Per unit cost of DG, electricity=22.83
(Note: we are considering 70% from electricity and 30% from DG for per unit cost)
Total energy generated by solar per year (units) = 46530 units or KWH
Total savings per year ( in rupees) = 632436
Project cost: 2800500
Payback period will be around year= 4.43 years
- Hidden Savings:
a) Night Sleep Mode: As mentioned above the night sleep mode has resulted in hidden savings which when calculated amount to savings of more than 50,000 per annum.
b) Employee Productivity: Frequent power cuts cause the shutdown-restart delay of computers, loss of concentration, and a general loss of productivity which cannot be measured in terms of money. All this is avoided by an un-interrupted supply.
c) Lesser load on ACs: The Sun rays falling directly on the terrace causes it to heat up and increase the pressure on the air-conditioners cooling the floor below. The solar panels structure causes it to naturally bring down the temperature by providing shade.
d) No more Diesel Pilferage: A lot of human effort to bring (transport costs) and store (storage space) the diesel whilst ensuring that theft does not occur (precious man-hours) was required earlier. Not anymore.
e) Exporting to the grid through net metering: Once the State electricity board allows for Grid export then Holidays, lean load days and winter days will result in a faster payback period through the feature of grid export via net metering.