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A heat pump is considered as a passive solar thermal system that can save up to half of what you usually spend for the diesel boiler. Let us consider this very simple example. A 4-star hotel was using a diesel boiler that consumed 40 liters of diesel, running  8 hours a day for the generation of hot water at 80 degrees centigrade. Now, let’s see what difference it would make if we replace the diesel boiler with a heat pump.

Calculating Boiler Capacity Installed

First of all, we will calculate the heating capacity of a diesel boiler installed in the hotel using the formula

where

m is the fuel consumption rate. i.e., 40 liters for 8 hours a day

CV is the calorific value of the diesel. i.e., 9500 kilocalories per liter

n is the efficiency of diesel boiler i.e., 80%, calculating which gives the value of installed capacity of the boiler as 44 kilowatts.

Calculating Heat Pump Capacity Needed

The next step is the selection of heat pumps. If we use our standard model of 28-kilowatt heat pump, whose power input is 10 kilowatts, we should select two numbers to get the desired heating output of 44 kilowatts.

In addition to this, we have to add the auxiliary load consumption by the circulation pumps which usually ranges from 1 to 1.5 kilowatts. So, the total power input could be 20 kilowatts + 1.5 kilowatts which is 21.5 kilowatts. Now let’s move to the savings part.

Comparing Running Costs of Diesel Boiler With Heat Pump

First of all, we will calculate the operating cost of the diesel boiler for one day. i.e., 40 liters of diesel used per day x cost of diesel per liter i.e., 70 rupees, which gives the value of 2800 rupees.

Now calculating the operating cost of heat pump for one day i.e 21.5 kilowatts x  8 hours of operation x 8.5 rupees i.e, the unit cost of electricity, which gives a value of 1460 rupees.

The difference between these two values, i.e, 1340 rupees, is our savings per day!

Payback Period, Financial and Environmental Savings

If you calculate the savings for one year by multiplying it with 360 days, their annual saving would be 4,82,400 rupees. Finally, if they start using heat pumps right now, the return of investment would be 1.5 to 2 years. By using a heat pump, they not only save the money but also reduce the emission of carbon dioxide to the atmosphere.