Rooftop photovoltaic (PV) systems for industrial halls - achieving economic benefit via lowering energy demand

Author(s): 
Bruno Lee, Marija Trcka, Jan L.M.Hensen (Eindhoven University of Technology)

Industrial halls are characterized by their relatively high roof-to-floor ratio, which facilitates ready deployment of renewable energy generation, such as photovoltaic (PV) systems, on the rooftop. PV systems could be readily deployed and attached to the rooftop with no special requirement on or alteration to the building design, but they require high capital investment. In order to promote wider deployment of PV systems in the hope that wider adoption will lower the cost of deployment in the future, government policies come in different forms of economic incentives to compensate the high investment cost. Out of these, feed-in tariff (FIT) is the most common form of such incentive. In this paper, the focus is to find the optimized building design options on demand side parameters that will maximize the economic benefit of the PV system investment. The energy consumption due to the demand of space conditioning will also be presented, since design options that yield the maximum economic benefit might not consume the least energy, or vice versa. This paper is based on the cost–benefit analysis in which the monetary return due to electricity generation of PV system (based on savings in energy cost or income from selling of the exported electricity at FIT), is stacked against the annualized cost of the PV system investment.

In order to benefit from the net FIT scheme, the building has to be carefully designed to lower the energy demand such that the PV system can generate more surplus electricity at more hours and export back to the grid at the higher FIT rate. Cost–benefit analysis is therefore an integrated evaluation of both energy and economic aspects.

Net benefit as optimization progresses across 20 generations of 50 configurations each

Net benefit and the corresponding energy consumption for HVAC for the optimized design solutions

The building energy performance simulation program TRNSYS is used to perform the energy analysis. For each building configuration, the hourly energy demand will be imported to a custom built MATLAB function that will calculate the balance between the energy demand and the electricity generation, at each hour. These two software have been coupled by means of modeFRONTIER in order to perform a single-objective optimization (with MOGA-II) on investment return has been performed to study the cost effectiveness among different options in lowering energy demand, demonstrated with a case study of a warehouse. From this particular case study, a 55% difference in energy consumption for HVAC is observed between the optimized design solutions and the less effective ones. Though energy consumption for HVAC is only a fraction of energy used for all processes, the absolute amount is still a significant sum that makes it worthwhile to investigate energy saving possibilities.

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