Grid-Connected Microgrid Cuts Campus Emissions by 99.3%

Researchers at Pabna University of Science and Technology in Bangladesh have developed a high-renewable hybrid microgrid that significantly reduces lifecycle carbon emissions for institutional loads. By integrating solar photovoltaic and wind turbine generation with grid interaction, the system achieves a net lifecycle emission intensity of 4.53 grams of CO2-equivalent per kilowatt-hour. This represents a 99.3% reduction compared to the conventional grid-only base case, which emits 620 grams of CO2-equivalent per kilowatt-hour. The study, published in Environmental Sciences Europe, combines techno-economic optimization with a cradle-to-grave lifecycle assessment to evaluate both the economic and environmental performance of the proposed design.

The microgrid was specifically designed for a college-scale load profile characterized by daytime-dominant energy consumption and weekday-weighted usage patterns. The site, located in Pabna, Bangladesh, experiences a subtropical climate with high solar irradiance and moderate wind availability. The average daily energy demand for the campus is 3,175 kilowatt-hours, with a peak load of 548.55 kilowatts. This load profile aligns closely with peak solar generation, resulting in high self-consumption of on-site photovoltaic output. The temporal alignment between demand and renewable generation makes solar-led hybrids particularly effective for this specific institutional load class.

The optimal configuration identified through HOMER Pro optimization consists of 780 kilowatts of solar photovoltaic capacity, 48 wind turbines with a total rated capacity of 244.8 kilowatts, and a 463-kilowatt bidirectional converter. The system operates under a net-metering arrangement, where surplus renewable energy is exported to the utility grid, and deficits are imported from the grid. This grid-connected design does not include electrochemical battery storage, as the utility grid serves as the primary balancing resource. The absence of storage is a consequence of the continuously available grid, which performs the temporal energy-shifting function that a battery would otherwise provide under islanded conditions.

Economic analysis indicates that the hybrid system achieves a low cost of energy of $0.0218 per kilowatt-hour, which is the average cost of producing one kilowatt-hour of electricity over the project lifetime. The net present cost of the system is $523,143, with an annual operating cost of $3,624. The renewable fraction of the energy mix is 81.7%, with solar photovoltaic contributing 63.4% of the total annual energy production and wind turbines contributing 19.3%. Grid purchases account for the remaining 17.4% of the energy supply. The economic viability is supported by a return on investment of 17.4% and an internal rate of return of 21.8%, with a simple payback period of 4.50 years.

The lifecycle emission assessment follows ISO 14040 and ISO 14044 guidelines, adopting a cradle-to-grave system boundary that encompasses six stages: manufacturing, transportation, installation, operation, maintenance, and end-of-life decommissioning. The functional unit is defined as one kilowatt-hour of electrical energy delivered to the load over a 25-year project horizon. Emissions are expressed in kilograms of carbon dioxide equivalent using IPCC AR6 100-year Global Warming Potential characterization factors. The assessment covers six pollutant species: carbon dioxide, sulfur dioxide, nitrogen oxides, carbon monoxide, particulate matter, and unburned hydrocarbons.

On a gross basis, which includes both embodied and operational emissions, the lifecycle emission intensity of the proposed configuration is 264.9 grams of CO2-equivalent per kilowatt-hour. This represents a 57.3% reduction relative to the grid-only base case. The embodied emissions, which include the environmental burden of manufacturing, transporting, installing, and maintaining the components, total 2,887.4 tonnes of CO2-equivalent. Solar photovoltaic is the largest contributor to embodied emissions at 1,372.8 tonnes, followed by the wind turbine array at 1,046.5 tonnes and the converter at 468.1 tonnes. Manufacturing dominates the embodied emission profile, accounting for approximately 82% of the total for solar photovoltaic components.

When the renewable electricity exported to the grid under the net-metering scheme is credited as avoided emissions, the net lifecycle intensity drops significantly to 4.53 grams of CO2-equivalent per kilowatt-hour. This net accounting perspective treats each exported kilowatt-hour as displacing grid generation at the prevailing grid emission factor. The annual grid exports of 486,686 kilowatt-hours displace approximately 301.7 tonnes of CO2 per year, while the annual grid imports of 308,871 kilowatt-hours result in approximately 191.5 tonnes of CO2 emissions per year. This net annual avoided emission of 110.2 tonnes of CO2 allows the system to recover its embodied carbon debt within approximately 3.5 years.

The study highlights the importance of distinguishing between gross and net lifecycle emissions, particularly in the context of a decarbonizing grid. As the grid emission factor decreases over time, the avoided-emissions credit associated with exported electricity diminishes proportionally. In the limiting case of a fully decarbonized grid, the net lifecycle intensity converges toward the gross intensity of 264.9 grams of CO2-equivalent per kilowatt-hour, which is dominated by embodied emissions. Therefore, the exceptional net performance reported in this study is characteristic of a high-renewable microgrid operating within a presently carbon-intensive grid. The gross figure represents a more durable long-term metric as the surrounding grid decarbonizes.

Sensitivity analysis was conducted to evaluate the robustness of the proposed design under variations in meteorological and economic parameters. The analysis varied solar irradiance, wind speed, ambient temperature, discount rate, and inflation rate across defined ranges. Solar irradiance and wind speed were identified as the most influential parameters affecting system economics. Increasing solar irradiance from 60% to 140% of the base value decreased the cost of energy from $0.04502 to $0.01349 per kilowatt-hour. Conversely, increasing temperature negatively impacted system economics, raising the cost of energy from $0.01958 to $0.02408 per kilowatt-hour. The nominal discount rate also exhibited significant effects, shifting the cost of energy from $0.01256 to $0.0331 per kilowatt-hour.

The research addresses several methodological gaps in the existing literature, where techno-economic optimization and lifecycle assessment are often conducted separately. Most prior studies quantify only operational emissions returned by optimization software, omitting stage-wise embodied burdens and avoided emissions from net-metered exports. This study integrates these elements into a unified workflow, providing a more comprehensive framework for sustainable energy planning. The findings demonstrate that college-scale institutional loads are structurally well-suited to high-renewable microgrids and can serve as scalable pathways toward ultra-low-emission campus electrification.

The study has limitations, including the assumption of continuous grid availability and the use of long-term averaged meteorological data for operational emission estimates. The impact of high-frequency atmospheric effects, such as cross-continental dust transport, on solar irradiance and PV energy yield is represented only in an aggregated form. Future work will extend the framework by incorporating battery and hydrogen-based storage for islanded resilience, integrating deep-learning-based forecasting for real-time energy management, and validating the optimized configuration through pilot-scale field deployment. These extensions aim to bridge the gap between simulation-based design and operational performance under real-world conditions.

The integration of lifecycle assessment with microgrid optimization provides actionable metrics for policy and decision-making. The carbon break-even year, emission intensity, and avoided-emission credit offer tangible measures of environmental performance that operational-only assessments cannot provide. By quantifying the full lifecycle impact of the microgrid, the study offers evidence for prioritizing educational and institutional campuses as early sites for microgrid deployment in Bangladesh and comparable developing economies.

Subject of Research: Lifecycle emission assessment of a grid-connected PV-Wind hybrid microgrid for a university campus in Bangladesh

Article Title: Lifecycle-aware microgrid design: quantifying embodied, operational, and avoided emissions in a grid-connected PV–Wind system

Article References: Azam, M. E., Ali, M. F., Alam, M. S., Obaidi, O., Ali, M., & AlAqil, M. A. (2026). Lifecycle-aware microgrid design: quantifying embodied, operational, and avoided emissions in a grid-connected PV–Wind system. Environmental Sciences Europe, 38(1), Article 174. https://doi.org/10.1186/s12302-026-01501-w

Image Credits: AI Generated

DOI: 10.1186/s12302-026-01501-w

Keywords: microgrid, lifecycle assessment, renewable energy, carbon emissions, solar photovoltaic, wind turbine, Bangladesh, energy optimization, net metering, sustainability, Lifecycle-aware, design