Case Study

Problems faced:

1. Erratic Supply and poor quality of Grid
2. Ever increasing cost of diesel and maintenance of Diesel Generator Sets
3. DG Set running at less than 30% rated capacity causing a decrease in life of the DG Set
4. Loss of productivity among employees
5. A sun exposed terrace causes extra strain on the Air conditioners
6. Frequent power cuts of 10 minutes to 4 Hours
7. Increasing cost of electricity with Time-Of-Day (TOD)
8. Very High fixed charges bringing the electricity bill to > ₹ 9.50 Per Unit ($ 0.14 per unit)
9. Typically the peak load does not end at 4 pm and electricity charges can be as high as 15-20% in this TOD of 5pm- 10pm regime.

Method:5 Things were to be considered before designing the Solar Power System.

• Aesthetics of the building
• Extra space utilisation of the terrace
• Ergonomics of the installation keeping future maintenance in mind
• Type of inverter system to cater to sensitive server loads and increasing diesel costs
• Payback period

Solution:

With discussions between the architect and the design team, an angled tin roof was constructed upon which the solar panels were installed with a total capacity of 30KWp.  A metal mesh to walk about was also put up for cleaning purposes.

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: 

1. 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. 

2. 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)

3. 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.