Engineering case study · Rajbanshi Nagar, Patna
LNJP Orthopaedic Hospital hybrid solar hot-water solution.
A two-zone concept combining an 80-collector FPC field, large insulated storage, air-to-water heat pumps, duty/standby circulation and PLC/HMI control for resilient institutional hot-water service.
40 FPCZONE 1
→5,000 LTANK 1
+46 kWHEAT PUMP 1
40 FPCZONE 2
→5,000 LTANK 2
+46 kWHEAT PUMP 2
This page describes the retrieved design-review / pre-installation basis. It does not claim final as-built quantities, commissioning completion, measured savings, outlet temperature or operating performance. Those require approved as-built records and site data.
The requirement
Institutional hot water needs redundancy and recovery.
A hospital load varies by time and function. The solution therefore separates the plant into two independent 5,000-litre trains so one zone can be serviced while the other remains available, subject to distribution interconnection and operating procedure.
Solar-first architecture
Forty FPC collectors charge each tank zone directly.
The retrieved basis uses direct solar-to-tank charging with no solar heat exchanger or solar secondary pump. Compatibility with the selected FPC, water chemistry and scaling protection must be confirmed before construction.
Hybrid recovery
Heat pumps supplement—not replace—the solar field.
One 46 kW design-basis air-to-water heat pump pairs with each tank train. Controls can enable recovery when tank temperature, time schedule and safe operating conditions require it. Exact model and performance must follow the approved datasheet.
Hydraulics and resilience
Five duty/standby pump sets support critical circulation.
The philosophy totals ten pumps: solar Zone 1 and Zone 2, heat-pump circulation for each train, and a common domestic-hot-water return set—each one working plus one standby. Final flow and head remain hydraulic design outputs.
Control and safety concept
PLC/HMI turns equipment into an observable system.
- Collector, tank top/bottom, supply and return temperature sensing
- Flow switches, tank low-level and pressure protection
- Pump and heat-pump run/fault feedback
- Auto/manual modes, duty/standby changeover and alarms
- Water softener, expansion vessel, PRV/SRV, ARV, strainers, NRV and drains
- Mixing valve and insulated distribution/recirculation