Simulating Sudan's Climate in London: How We Solved Solar Efficiency Loss in Extreme Heat

Originally published 28 February 2026. Updated 3 August 2026 with quantified temperature-loss data and a comparison of our findings against cooling research published in 2025.

The Problem We Kept Running Into

A panel rated at 550 watts does not deliver 550 watts in a Sudanese June. Some afternoons it does not come close.

Sudan receives over 3,000 hours of sunshine annually, among the most favourable solar resources on earth. The irony our engineers kept confronting is that the same sun that makes the country ideal for solar generation actively degrades solar panel efficiency in extreme heat. The energy is abundant precisely when the equipment is least able to convert it.

We encountered this repeatedly while installing 37 off-grid solar systems across Sudan under an African Development Bank project. A system sized carefully on paper would underperform in the field during the hottest hours, which in an off-grid installation are often the hours of highest demand. Fans, pumps and refrigeration all peak in the afternoon, exactly when the array's output sags.

Anecdotes from the field are not evidence, though. Financiers and regulators do not approve design changes because an installation team noticed something. So we set out to measure the problem properly, and to test whether anything affordable could be done about it.

What Extreme Heat Does to Solar Panel Efficiency

Every solar module is rated under Standard Test Conditions: a cell temperature of 25°C and irradiance of 1,000 W/m². Those conditions describe a mild spring day in Europe. They do not describe Sudan.

Crystalline silicon panels lose output as cells warm beyond that reference point, a behaviour captured in the module's temperature coefficient. For most mainstream panels this sits between 0.30% and 0.50% of rated power for every degree Celsius above 25°C. The physics is unforgiving: higher cell temperatures increase the semiconductor's internal carrier recombination, dragging down voltage faster than the extra heat adds anything useful.

The compounding matters more than the coefficient. In Sudan, ambient temperatures regularly exceed 40°C, and a dark module under full irradiance runs 20°C to 30°C hotter than the surrounding air. Cell temperatures of 60°C to 70°C are routine, which translates to output losses of 10% to 15% or more against nameplate rating, sustained through the most productive hours of the day.

Rated conditions against Sudanese operating conditions. Source: MIMAH environmental chamber testing, London South Bank University.

Consider a rural clinic north of Khartoum running vaccine refrigeration on a 5 kW array. Lose 12% of output through the afternoon and the battery bank finishes the day short. Repeat that daily and either the cold chain fails or the system has to be oversized, and oversizing means panels, copper and batteries that a donor-funded budget must absorb. Heat is not an abstract efficiency problem. It is a costing problem on every hot-climate project we quote.

Output against nameplate rating at Sudanese operating temperatures. Source: MIMAH environmental chamber testing, London South Bank University.

This is the engineering constraint sitting under Sudan's wider solar opportunity: the resource is world-class, but capturing it means designing for the heat rather than around it.

Taking Sudan's Weather to London

Testing solutions in the field would have meant at least a year of data collection to account for seasonal variation and dust conditions, on sites that are difficult to access and instrument. We compressed that year into two weeks.

Through the Sustainable Innovation Programme at London South Bank University, we gained access to an environmental testing chamber capable of reproducing the temperature, humidity and irradiance profile of a Sudanese summer inside a laboratory in Southwark. Working with researcher Abdullah Qaban and LSBU's School of the Built Environment and Architecture, we designed controlled experiments that isolated the variables affecting hot-climate output.

The rig included a solar array simulating sunlight, a power inverter handling DC-to-AC conversion, load resistors to manage excess power, a solar power meter for radiation measurement, and a solar tester capturing electrical data. Because the chamber let us hold every condition constant except the one under test, we could attribute each change in output to a specific cause, something field testing can never fully achieve.

Facing a similar unknown in your own system's performance? Our renewable energy engineering team designs and validates systems for exactly these conditions.

What We Found

The first result confirmed the field observation with laboratory precision: as module temperature rose beyond rated conditions, electrical output declined in a predictable, measurable curve. That predictability matters. It means heat loss can be engineered for, not merely suffered.

The second result is the one that changed our designs. Applying water cooling combined with a fine layer of sand on the panel surface produced a measurable increase in efficiency under high-temperature conditions. The water draws heat out of the module directly, while the sand layer moderates surface temperature swings and extends the cooling effect between applications.

What makes this finding useful rather than merely interesting is the bill of materials. Water and sand are locally abundant in every region where we deploy. A cooling approach built on imported phase-change materials or specialised coatings would fail the test that matters most in Sudan: can it be sourced, installed and maintained by a local team without foreign currency? This one passes.

How Our Results Compare With the Wider Research

Since we ran our chamber tests, independent research published in 2025 has strengthened the case for active cooling in hot climates, and it is worth placing our findings in that context.

A 2025 experimental study of water cooling on PV modules in a hot climate recorded module temperature drops of roughly 29°C to 33°C, lifting electrical efficiency from 17.6% uncooled to 21.9% cooled. A broader 2025 review of next-generation PV cooling strategies found that passive approaches such as radiative coatings and phase-change materials typically recover 2% to 15% of efficiency, while active water-based methods deliver the largest temperature reductions, at the cost of water and pumping energy.

Our water-plus-sand result sits deliberately between those two families: an active method using the cheapest possible consumable, moderated by a passive layer that stretches each cooling cycle. For deployment regions where both water and budget are constrained, that trade-off is the point. The best cooling method on paper is worthless if a site cannot sustain it for 25 years.

Third-party validation matters here for a second reason. Evidence generated at LSBU, rather than in our own workshop, satisfies the regulatory and financing requirements that new technology approval in Sudan demands. When a lender asks why our hot-climate designs specify cooling provisions, we point to independent laboratory data, not marketing claims.

Measured effect of water cooling on module efficiency in a hot climate. Source: Experimental evaluation of water cooling effects on photovoltaic module performance in a hot climate, International Journal of Energy and Water Resources, Springer, 2025.

Why This Matters Beyond Our Projects

Solar efficiency loss in extreme heat is not a Sudanese peculiarity. It affects installations across the entire Sunbelt: the Sahel, the Arabian Peninsula, South Asia and northern Australia, the same regions where solar is expanding fastest.

Even a few percentage points of recovered efficiency compound enormously over a 25-year asset life. For a utility-scale plant, that compounding shows up in the financial model. For an off-grid system powering a clinic, a school or a water pump, it shows up as whether peak afternoon demand is met or missed.

We have since applied this thinking at scale. The Sudan Solarisation Programme, delivered for UNDP across 110 healthcare facilities in six states, and the Dongola integrated off-grid solar and pumping system in Northern State were both specified with hot-climate derating and cooling provisions built into the design, not bolted on after underperformance appeared.

Ready to pressure-test a design for a demanding climate? Talk to our engineers before the specification is locked, when these decisions are still cheap.

What Came Next

The partnership outlasted the experiment. Our work strengthened LSBU's renewable energy testing capability and gave the university's researchers direct industrial experience, and two further companies working on solar solutions for challenging climates have since joined the Sustainable Innovation Programme.

On our side, the findings now inform every hot-climate system MIMAH designs. Cooling techniques sit alongside panel selection weighted for temperature coefficient, mounting angles optimised for airflow, inverter specification with thermal headroom, and maintenance scheduling adjusted for dust and heat cycles. None of these decisions is glamorous. Together they determine whether a system installed this year is still meeting its load in year ten.

Building on Evidence

Sudan's electricity access gap, with roughly 40% of the population unconnected, will not be closed by equipment specified for European conditions and shipped south. It will be closed by engineers who understand local conditions, test their solutions rigorously, and design systems for decades of performance in punishing climates.

That is the working method this project cemented for us: observe the problem in the field, measure it in the laboratory, validate the fix independently, then build it into standard practice. The sun in Sudan is not going to get any cooler. Our job is to make sure the panels do.