Knowledge Centre – Passive Strategies

Solar Air Conditioning
Introduction
Case Study
Resources & Tools

Introduction

solar ac

Schematic diagram of a solar air conditioning system.  Typically vapor absorption machines or chillers are used in solar conditioning. Energy is saved by using the heat generated from the solar panels to regenerate the absorbent in the chiller.

Cooling loads in tropical countries like India peak during the hot summer season when solar radiation is available in abundance. Thus, application of solar cooling technology uses a renewable source of energy to reduce the cooling loads when air conditioning demand is at its annual high. Principle behind the functioning of solar cooling is the use of solar heat/ thermal energy to re-generate the refrigerant in absorption chiller or desiccant in a desiccant chiller.

Absorption chillers comprise of the following components:

  1. Evaporator: where the refrigerant evaporates at a very low pressure and temperature and is absorbed by the absorbent. The process results in extraction of heat from the refrigerant and provides chilled refrigerant as an output.
  2. Generator: The mixture of absorbent and refrigerant is then introduced in the generator. Steam or hot water produced through the solar panel devices is used to vaporize refrigerant.
  3. Condenser: The vaporized refrigerant will be cooled down in condenser and maintained at low pressure. This cooled refrigerant will be further used in evaporator for generation of chilled water for air conditioning.

Table: Advantages and disadvantages of evaporative cooling systems

Pros Cons
Attractive payback when configured with power generation and hot water heating Requires significant space for the solar panels and solar concentrators; thus suitable for large projects only
Low distribution losses in the range of 5 to 10 percent; conventional technologies is between 75-80 percent Cost almost twice as much as conventional chillers
Eliminate the use of CFC, HFC, and HCFC refrigerants Requires greater pump energy compared to electric chiller
System operations generates less noise and vibration Higher flow rate of condenser water required as absorption chillers have lower COP’s
High efficiency in triple effect absorption designs Requires large cooling tower capacity compared to electric chiller as larger volume of water is circulated

Case Study

Case study Solar Energy Center
Location Gurgaon, Haryana, India
Climate Type Composite
Building Type Office and residential
System Description Solar air conditioning100 kW cooling capacity standalone system is integrated with triple effect Vapour Absorption Chiller (VAC) and solar parabolic concentrators. The system is designed to meet cooling loads of 13 rooms at the centre. VAC can use steam, hot water, gas, kerosene or oil to run continuously. Chilled water is supplied at 7 °C through FCUs to all rooms. Solar collectors, with area of 284 sq. mt., deliver water at temperatures between 140 °C and 210 °C.
System Performance The integrated system is estimated to be 20 percent more efficient than VACs with no solar component. Co-efficient of Performance (COP) is 1.7, which is highest among the vapour absorption technology coupled with eco-friendly energy resource. System has built-in thermal energy storage using phase change materials. This allows it to supply cooling continuously.

Solar Energy Center
Source: PACE-D: HVAC Market Assessment and Transformation Approach for India

case study3

Solar Energy Center
Source: PACE-D: HVAC Market Assessment and Transformation Approach for India

Resources & Tools

Online Resources

  1. Absorption Chiller Guideline

Publications

  1. Advanced Design Guideline by the New Buildings Institute for the Southern California Gas Company, contract P13311, part of SoCalGas