RACA Journal I March 2026 www. refrigerationandaircon. co. za 21
ENERGY EFFICIENCY FEATURE SERIES
but the economics change. Fully off-grid warehouses are still the exception rather than the rule,” Bekker says.
What sets the De Deur installation apart is its adaptive capacity control, which dynamically links HVAC output to available solar and battery power – an industry first in South Africa.
In practical terms, the system receives real-time feedback from the solar inverter via analogue signals. The inverter communicates the current charging capacity of the solar array, and the VRF system responds by adjusting its own output accordingly.
“ If solar availability drops because of cloud cover, the air conditioning doesn’ t suddenly pull hard from the batteries. Instead, it steps down smoothly.”
For example, a reduction from 100 % to 90 % solar availability might result in HVAC capacity being reduced to around 80 %. Further reductions follow a stepped logic designed to maintain comfort while protecting the energy system. Only when solar availability drops below a defined threshold does the system shut down completely – a scenario that has never occurred at De Deur due to correct system sizing.
“ That’ s the real value of intelligence. You prioritise resilience and continuity instead of brute-force performance,” says Bekker.
MANAGING TECHNICAL RISKS OFF-GRID Operating off-grid introduces risks beyond HVAC equipment itself. One of the most significant challenges identified early on was power transition stability, particularly when integrating solar, batteries and generator backup.
In conventional buildings, rapid changeovers between generator and utility power – often occurring in less than a second – can cause severe voltage dips and inrush currents exceeding 500 amps, leading to premature equipment failure.
At De Deur, this risk was mitigated through carefully designed interlocks and a third-party time-delay system. When transitioning between generator and solar power, a 30-second delay is enforced before power is reapplied.
“ That delay allows voltages to stabilise and prevents damaging inrush currents. It’ s a small detail, but it makes a massive difference to long-term reliability.”
For developers and building owners, balancing higher upfront investment against long-term operational savings remains a challenge. Bekker notes that while regulatory pressure is increasing – particularly for public-sector buildings – many private developments still focus on short-term cost reductions.“ Too often, energy strategies stop at lighting upgrades,” he says.“ LEDs help, but HVAC is where the real energy is being used.”
Investing in inverter-driven, renewable-ready HVAC systems delivers compounding benefits: reduced peak demand, improved compatibility with solar and batteries, and greater operational resilience during grid instability.
“ In South Africa, resilience has a value that goes far beyond kilowatt-hours.”
A PROVEN, BUT UNDERUTILISED MODEL LG sees systems like Multi V5 as central to future hybrid PV, battery and grid-interactive strategies. The De Deur project has already been used as a regional case study in markets facing similar grid challenges.
Despite its technical success, however, Bekker remains realistic about adoption. Interest in solar-assisted HVAC surged during periods of severe load shedding but has softened as grid conditions stabilised.“ The model works. The challenge now isn’ t technology – it’ s mindset and investment priorities,” he says. For engineers and developers under pressure to deliver immediate energy reductions rather than aspirational net-zero targets, Bekker’ s advice is pragmatic.“ The first step is simple. Move away from constant-speed, on / off compressors to inverter technology. That alone delivers immediate gains.”
While some markets have shifted back toward chilled water systems, VRF remains better suited to solar integration due to its modularity and capacity control.“ Large chillers need massive solar and battery systems. With VRF, you can prioritise critical zones and manage energy far more intelligently.”
The De Deur project demonstrates that off-grid, solardominant HVAC is not theoretical. With efficiency-led design, intelligent controls and integrated planning, it is already achievable today under South African conditions.
“ And that,” Bekker emphasises,“ is where the real energy conversation needs to start.” RACA
Energy efficiency
I and S Workshops and Warehouse, located in De Deur, is a good example of a sustainable building practices.
RACA Journal I March 2026 www. refrigerationandaircon. co. za 21