Dynamic Operation of a Heat Exchanger in a Thermally Integrated Photovoltaic Electrolyzer

The outdoor operation of an up-scaled thermally photovoltaic electrolyzer (PV EC), constructed using a heat exchanger (HE) made of low-cost materials, compared to its nonintegrated counterpart to quantify heat transfer and its effects, is studied. Thermal coupling of the PV and EC can reduce the difference between their temperatures, benefitting device performance. Such devices can produce hydrogen at rooftop installations of small-to-medium-sized nonindustrial buildings. The devices are tested outdoors using automated real-time monitoring. Under approximate to 880 W m(-2) peak irradiance, they produced hydrogen at approximate to 120 and approximate to 110 mL min(-1) rate with and without HE, respectively, corresponding to about 8.5% and 7.8% solar-to-hydrogen efficiencies. During about 700 h of testing, the HE is beneficial at over approximate to 500 W m(-2) due to cyclic device operation. Under lower irradiance levels, pumping previously heated electrolyte through the HE increases the PV and reduces the electrolyte temperature, reducing the device performance. The HE increases the cumulative hydrogen production (approximate to 800 L from both devices), so even relatively modest heat transfer rates can improve the PV EC operation. Improving the HE should further increase the benefits, but additional measures may be needed to maximize the hydrogen production.

Automated summary

The study investigates the thermal transfer and its effects in an up-scaled thermally photovoltaic electrolyzer (PV EC) with a heat exchanger (HE) made of low-cost materials. The thermal coupling of PV and EC enhances device performance by reducing temperature differences. These devices can generate hydrogen on the rooftops of small-to-medium-sized nonindustrial buildings. Outdoor testing, using real-time monitoring, shows that under peak irradiance of approximately 880 W m(-2), the devices produce hydrogen at rates of approximately 120 mL min(-1) with HE and approximately 110 mL min(-1) without HE, corresponding to solar-to-hydrogen efficiencies of about 8.5% and 7.8%, respectively. The HE is beneficial at irradiance levels above approximately 500 W m(-2) due to cyclic device operation. However, under lower irradiance levels, pumping previously heated electrolyte through the HE reduces device performance. Despite this, the HE increases cumulative hydrogen production (approximately 800 L from both devices), indicating the potential for improving PV EC operation even with modest heat transfer rates.