Solar Air-Conditioning: Solar Case Study

This solar air conditioning case study pertains to the sizing of an indoor solar conditioning system that uses an absorption chiller unit operating with water and lithium bromide (Li Br) for a hypothetical 3 bedroom Villa or house.



Hypothetical Villa Solar Air-Conditioning Case Study



Input Data for Sizing:

Climate data for the calculation of solar radiation related to a selected hot climate city. The data relates to a hypothetical two-family dwelling (or large apartment) and to the building’s energy performance as assumed below.

Indoor conditioned volume	562,5 [m3]
Net surface area	187,5 [m2]
Maximum heat loss	100 [kWh/day]

Month	Average daily air temperature C°	Average daily cooling demand kWh/day
January	20.7	54
February	20.6	53
March	22.3	59
April	25.8	71
May	30.1	86
June	32.2	93
July	33.6	98
August	34.2	100
September	32.9	96
October	30.2	86
November	26.8	75
December	23.2	62

*estimated

Design Stage for Solar Air-Conditioning Case Study:

The sizing calculations of the absorption chiller and the solar field was determined taking into account a daily design energy demand due to heat loss of approximately 100 kWh.

Area Required for Solar Air Conditioning

Main Equipments Required for Solar Air Conditioning

As you can see from the above image and from the previous post how solar air conditioning works, there are certain things you need to account for to see if your building will be able to accommodate the solar air conditioning equipment such as:

Roof Area Required for Panel Installation on Roof:

Harvesting solar energy via solar thermal panels that is used to feed hot water to the absorption chiller requires a lot of space on the roof or open space. This is not like thermal panels for water heating where 40 Deg C will be sufficient for a shower. The absorption chiller requires input temperature of around 80 Deg C and above for it to operate efficiently and you would get a 6 Deg C chilled water output.

Before Considering Solar Air Conditioning

Talking about solar air conditioning and its advantages is great. However, there are certain considerations that you have to think about before considering installation of a solar air conditioning. After all, you may not need to spend that much money to buy a solar air conditioner.

For argument sake, take an existing 4 story building as your model since the rate of return on initial investment is faster compared to a single story building and assume your area is a hot climate with average temperature 35 deg C.

With such temperature, your building would act as a heat radiating furnace! Surprised I believe? Definitely, your existing building absorbs heat during the day and in turn you switch on your conventional air conditioner in order to bring the temperature down. Why? 

The building was never designed to be energy efficient from the first place and you spend your money on cooling to stay comfortable.

If this is the case in your building, then installing a solar air conditioner for cooling the building is worthless and you would be throwing your money away! What should you do?

Solar Air Conditioning – How Solar Air Conditioning Works?

Before talking about how solar air conditioning and solar cooling works, one must have some basic information about passive solar water heating. The passive solar water heating basically uses a pump for circulating heated liquid in solar collectors. The heated liquid is then used for solar air conditioning and cooling using Lithium Bromide (Li-Br) absorption chillers.

To make it easy on you to understand how solar air conditioning and cooling works, an illustrative diagram is shown below to explain the process for passive solar water heating. An explanation will follow on how to get solar air conditioning results. i.e., Absorption chillers use heat for cooling.

Passive Solar Water Heating - Forced Circulation

The diagram above shows a passive (forced circulation) system that uses a number of solar collector plates (or can be vacuum tubes) to harvest free energy from sun rays.

A liquid absorbent (Glycol or water) transfers heat from the solar thermal collector panels. A pump forces