Heating and cooling supply for a building · four options compared

Four cooling options

Calculates annual gas, electricity and water use, capital cost, payback and the 10-year total cost of ownership. All amounts include VAT, as on the customer’s invoice. In three of the options condenser heat is rejected by a wet cooling tower: for absorption machines and centrifugal chillers a dry cooler cannot reach the required condensing temperature in summer.

—

—

When another option takes the lead

The parameter value at which the runner-up overtakes the leader, with everything else unchanged.

Cumulative cost over 10 years

Capital cost plus cumulative operating cost, with tariff escalation.

Where the money goes each year

Operating cost by item: gas, electricity, water with water treatment.

Gas Electricity Water and chemicals

Monthly load

Net demand of the building, the same for all four options.

Heat, MWh Cooling, MWh

What is behind the numbers

Equipment list and annual resource use for each option.

How it is calculated

  • Heat. Average monthly load is proportional to the temperature difference: peak load is multiplied by the ratio of (indoor minus monthly average) to (indoor minus design outdoor), then by the hours in the month, and divided by the distribution, control and emission efficiencies.
  • Cooling. Rated capacity × average load × operating hours in months warmer than the set threshold.
  • Wet cooling tower. Condenser water flow is based on a 5 °C range (32/27 mode), pumps on flow and head, fans on specific power. Make-up including blowdown is about two litres per hour per kilowatt rejected; water treatment is added to the water cost.
  • Hot-water absorption chiller. The boiler house must cover both space heating and the heat for the machine’s generator, so its capacity is sized for the larger of the two. In summer the boiler runs at 90 °C and does not condense, so its efficiency drops.
  • Packaged chiller. No cooling tower, no water treatment, no plant room, but the COP is half as good, and the whole difference goes into the electricity bill and the grid connection fee.
  • All prices include VAT. Equipment, tariffs and totals are the amounts the customer sees on the invoice. You can replace any price with your own in the left panel; the result updates instantly.
  • What is not included. Plant rooms, flues, the gas pipeline and gas supply limits, redundancy, service and repairs. These are estimated separately for each site.