Solar-Powered Absorption Cooling System Tested for Pakistani Homes — TRNSYS Analysis Shows Promising Results for Rawalpindi

A new technical study published in Engineering Post by Engr. Tayyeb Altaf, HVACR Instructor at Government College of Technology (GCT) Rawalpindi, demonstrates that solar-powered absorption air-conditioning is technically viable for single-family homes in Pakistan's climate. Using the industry-standard TRNSYS transient-energy simulation platform with R-32 refrigerant as the heat-exchange medium, the study models a five-loop residential cooling system tailored to Rawalpindi-equivalent conditions.

The technical setup

The simulation models a complete solar-absorption cooling system with five integrated thermal loops:

• Loop 1 — Solar collection: evacuated-tube glass solar collectors with R-32 as the heat-exchange medium, paired with a heat storage tank for thermal buffering across cloud-cover or low-irradiance periods.
• Loop 2 — Hot-water-stream absorption chiller: the core refrigeration cycle that uses thermal energy (instead of compressor electricity) to drive the cooling process.
• Loop 3 — Cooling tower water circuit: rejects waste heat from the absorption chiller to the ambient environment.
• Loop 4 — Chilled water to the chiller: distributes the cooling effect from the absorption unit toward the cold-side of the system.
• Loop 5 — Air delivery to the room: the final stage that conditions and circulates cooled air to the living space.

What the simulation found

The TRNSYS results for the Rawalpindi climate envelope showed:

• Collector outlet temperature: averaged 100°C throughout the simulated month — well within the operating range required by absorption chillers and demonstrating that evacuated-tube collectors can deliver consistent thermal output in Pakistan's solar irradiance conditions.
• Collector energy contribution: averaged 2,000 kJ/hr of useful thermal energy addition — sufficient to drive the absorption cooling cycle through the cooling-demand window of a typical Pakistani residential daytime.
• Room temperature achieved: 24°C — within the comfort band that mainstream residential air conditioning targets, validating that the solar-absorption approach can deliver thermal comfort comparable to conventional electric-driven cooling.

Why this matters for Pakistani electricity demand

Pakistan's residential electricity demand peaks heavily in summer cooling hours — typically the 1 PM to 11 PM window when ambient temperatures and AC duty cycles are highest. Conventional vapour-compression AC systems are exactly the load that drives the country's evening peak and the marginal furnace-oil and LNG-fired generation that sets the highest fuel cost adjustment on monthly bills.

Solar-driven absorption cooling addresses this structurally. Because the cooling cycle is driven by solar thermal energy rather than grid electricity, every kWh of cooling delivered via absorption represents a kWh not pulled from the grid — and specifically not pulled during the daylight hours when solar resource is strongest and grid generation cost (per the merit order) is highest. The technology shifts cooling load off the electrical grid altogether.

The R-32 refrigerant choice

The study's use of R-32 as the heat-exchange medium is notable. R-32 has a substantially lower global warming potential (GWP) than older HFC refrigerants while delivering competitive thermodynamic performance — making it the global industry standard direction for new residential and light-commercial cooling installations. Validating R-32 in a solar-absorption application keeps the system aligned with international refrigerant-phase-out trajectories.

Practical deployment considerations

While the TRNSYS simulation validates technical feasibility, real-world deployment in Pakistani homes faces three practical constraints:

• Upfront cost — solar-absorption systems carry significantly higher capital cost than conventional split-AC plus rooftop PV. The payback period needs careful analysis at current electricity tariffs.
• Service ecosystem — Pakistan's HVACR contractor base is well-trained on vapour-compression but has limited experience with absorption chillers. Skill-building and service-network development would need to accompany any meaningful deployment scale-up.
• Roof area requirements — evacuated-tube collectors require dedicated roof space, competing with PV panels for the same area on Pakistani residential rooftops.

The research-into-deployment opportunity

The Altaf study fits into a broader pattern of Pakistani academic research producing technically-rigorous foundations for renewable energy deployment that the policy and industry layers can then build on. NEECA, AEDB, and university energy-research centres collectively have substantial publication volume on solar-driven cooling, but the path from peer-reviewed simulation to commercial deployment in Pakistani homes remains weak. Bridging that gap is one of the higher-leverage interventions available to the federal renewable-energy policy machinery.