Technical Performance of a Grid-Connected Net-Positive Building in Nigeria's Hot-Humid Climate

Abstract

The building sector consumes over 30% of total global energy and accounts for about 40% energy related carbon emissions. This has drawn attention to high-performance buildings concept as a potential means of carbon emission reduction in the housing sector. However, most literature in high-performance buildings emanates from temperate climates. Limited literature on the applicability of high-performance building initiative in hot climates characterized with high cooling loads and unstable grid electricity. This study assessed a grid connected net-positive building in Abuja, Nigeria, using twelve months’ operational data and comparing its technical performance against a traditional building of same size, through which the annual energy balance, cooling system performance under different efficiency assumptions, thermal comfort using standard metrics and grid interaction patterns were assessed. The analysis revealed that the building generates 22,100 kWh annually and consumes 18,450 kWh showing a surplus energy advantage of 3,650 kWh. Despite this annual surplus, the building also imported a total of 4,980 kWh from the grid, while exporting 8,650 kWh, this result shows a mismatch between demand and energy generation. The refrigerant flow system that operated at a coefficient of performance of 4.2 achieved a cooling energy intensity of 30.7 kWh per square meter, compared to 40 kWh for conventional split systems. While the efficiency gain vanished at a coefficient of performance (COP) of 2.8, thereby emphasizing the need for equipment maintenance. The thermal comfort in the net-positive building showed a predicted mean vote of 0.6 from a neutral point with 18% predicted percentage dissatisfied in comparison to +1.8 and 68% for conventional building. However, the net-positive building missed the stipulated ideal target of ±0.5. The study concludes that high-performance buildings are technically viable in hot climates, but the performance is dependent on equipment choices, maintenance practices and load management strategies that are criteria for achieving optimum performance, as well as the building envelopes or the size and quality of the solar array.