• Energy Research

Knowledge of PV system characteristics is needed in different regional PV modelling approaches. It is the aim of this paper to provide that knowledge by a twofold method that focuses on (1) metadata (tilt and azimuth of modules, installed capacity and specific annual yield) as well as (2) the impact of shading. Metadata from 2,802,797 PV systems located in Europe, USA, Japan and Australia, representing a total capacity of 59 GWp (14.8% of installed capacity worldwide), is analysed. Visually striking interdependencies of the installed capacity and the geographic location to the other parameters tilt, azimuth and specific annual yield motivated a clustering on a country level and between systems sizes. For an eased future utilisation of the analysed metadata, each parameter in a cluster was approximated by a distribution function. Results show strong characteristics unique to each cluster, however, there are some commonalities across all clusters. Mean tilt values were reported in a range between 16.1° (Australia) and 35.6° (Belgium), average specific annual yield values occur between 786 kWh/kWp (Denmark) and 1426 kWh/kWp (USA South). The region with smallest median capacity was the UK (2.94 kWp) and the largest was Germany (8.96 kWp). Almost all countries had a mean azimuth angle facing the equator. PV system shading was considered by deriving viewsheds for ≈48,000 buildings in Uppsala, Sweden (all ranges of solar angles were explored). From these viewsheds, two empirical equations were derived related to irradiance losses on roofs due to shading. The first expresses the loss of beam irradiance as a function of the solar elevation angle. The second determines the view factor as a function of the roof tilt including the impact from shading and can be used to estimate the losses of diffuse and reflected irradiance.

The power system requires an additional amount of flexibility to process the large-scale integration of renewable energy sources. Community Energy Storage (CES) is one of the solutions to offer flexibility. In this paper two scenarios of CES ownership are proposed. Firstly, an Energy Arbitrage (EA) scenario is studied where an aggregator aims to minimize costs and CO2-emissions of an energy portfolio. Secondly, an Energy Arbitrage - Peak Shaving (EA-PS) scenario is assessed, which is based on a shared ownership between a Distribution System Operator (DSO) and an aggregator. A multi-objective Mixed Integer Linear Programming (MILP) optimization model is developed to minimize the operation costs and CO2-emissions of a community situated in Cernier (Switzerland), using different battery technologies in the CES system. The results demonstrate a profitable system design for all Lithium-ion-Batteries (LiBs) and the Vanadium Redox Flow Battery (VRFB), for both the EA and EA-PS scenarios. The economic and environmental performance of the EA-PS scenario is slightly worse compared to the EA scenario, due to power boundaries on grid absorption and injection to achieve peak shaving. Overall, the differences between the EA and EA-PS scenarios, in economic and environmental performance, are small. Therefore, the EA-PS is recommended to prevent problematic loads on the distribution transformer. In addition, the Pareto frontiers demonstrate that LiBs perform best on both economic and environmental performance, with the best economic and environmental performance for the Lithium-Nickel-Manganese-Cobalt (NMC-C) battery.

Abstract Residential demand profiles typically demonstrate a mismatch between energy demand and PV supply. Different solutions are proposed, such as demand side management and energy storage systems. Nevertheless, costs and environmental impacts of some technologies (e.g. batteries) are high. This paper proposes two system designs: Home Energy Storage (HES) and Community Energy Storage (CES). Besides electricity storage, heat storage is used in the two system designs to supply domestic hot water and space heating. Furthermore, the trade-offs between the different storage mediums in relation to costs are analyzed. To achieve that, different methodologies are used to size the electricity and heat storage mediums for HES and CES. Next, a multi-objective mixed integer linear programming model is developed to optimize the operation costs and CO 2 -emissions for each system design. After that, the model is tested on a residential community situated in Cernier (Switzerland). The results demonstrate that CES performs better than HES on economic and environmental performance due to economies of scale and the optimally sized storage capacity of the battery in CES. Currently, none of the proposed system designs is economically feasible. However, the sensitivity analysis shows that a profitable system design can be obtained for both HES and CES, when the electricity storage (i.e. battery storage) size is reduced and the heat storage (i.e. water storage tank) size is increased.

In this paper, we propose using marginal emission factors instead of average emission factors for determining the impact of adding variable renewable electricity to the generation mix. Average emission factors assume constant emissions over time, which does not reflect reality. Therefore, they cannot be used for e.g. accurately determining the mitigated CO2 emissions by renewables, or for scheduling shiftable loads in order to have the lowest CO2 emissions. To solve this, we provide a method to construct the marginal emission profiles via the merit order and demonstrate the method by composing these for the case of the Netherlands. Using this method, we re-evaluate the CO2 impact in 2014 of photovoltaic-generated electricity to be 0.42 Mt - compared to 0.36 Mt using the average emission factor - and for wind-generated electricity to be 3.6 Mt instead of 2.9 Mt CO2 (an increase of 14.3% and 24.2%, respectively). Furthermore, we show the impact of CO2 price on the merit order and show that even high CO2 prices of 50 to 75 €/tCO2 are not sufficient to phase-out new coal-fired power plants.

AbstractFloating solar photovoltaics (FPV), whether placed on freshwater bodies such as lakes or on the open seas, are an attractive solution for the deployment of photovoltaic (PV) panels that avoid competition for land with other uses, including other forms of renewable energy generation. While the vast majority of FPV deployments have been on freshwater bodies, in this paper, we chose to focus on offshore FPV, a mode of deployment that may be particularly attractive to nations where the landmass is constricted, such as is the case in small islands. There is a wide perception that seawater cooling is the main reason for the enhanced performance of offshore FPV panels. In this paper, a worldwide assessment is made to validate this perception. To this end, a technology‐specific heat transfer model is used to calculate PV system performance for a data set of 20 locations consisting of one system located on land and another one offshore. The analysis assumes that the floating offshore panels are placed on metal pontoons and that all panels are based on monocrystalline silicon technology. Our analysis shows that the energy yield difference, between land‐based and offshore systems, for the time period of 2008 and 2018, varies between 20% and −4% showing that offshore FPV yield advantages are site‐specific. In addition, the effect of other environmental factors, namely, irradiation level difference, ambient temperature, wind speed, precipitation, and sea surface temperature, is studied in this paper, which leads to the formulation of two different regression models. These can be used as a first step in predicting yield advantages for other locations.

AbstractThis article describes the method of deriving Global Horizontal Irradiance (GHI) from combining power measurements with static meta data (tilt, orientation, brand/type) of rooftop photovoltaic (PV)‐systems. This inverse PV model implements a forward yield model that is based on a modified Orgill and Hollands decomposition model and the Perez transposition model for irradiance. The forward as well as the inverse PV model were validated with DC power measurements of four different mono‐ and polycrystalline modules combined with weather station data (2 minute resolution data over a period ranging from the 11th of June through the 24th of August 2014). The bias‐corrected forward PV model shows a best (r)RMSE of 16.0 W (15.1%) with a (r)MBE of −1.67 W (−1.57%) for one of the polycrystalline modules. The bias‐corrected inverse PV model shows a best (r)RMSE of 65.6 Wm−2 15.1% with a (r)MBE of 0.994 Wm−2 (0.229%) for one of the polycrystalline modules. Similar results were obtained for the three other modules.

The Maldives is one of the most vulnerable countries to the projected impacts of climate change, due to a combination of the small sizes of the islands and their low height above sea level. Like other small island developing states, the Maldives depends overwhelmingly on petroleum imports for their electricity production, which creates serious economic and financial difficulties. The Government of Maldives is therefore committed to promote sustainable energy and has been actively pursuing several inter-related initiatives to overcome the existing barriers to the utilization of renewable energy technologies. To assist this, the quantification and evaluation of the potentials of available solar and wind resources in the country for electricity applications has been performed. The hybrid system design tool HOMER has been used to create optimal renewable energy (RE) system designs. In order to evaluate these different RE alternatives a multi-criteria analysis is performed using a number of criteria that are likely to be decisive in implementation decisions. The evaluation shows that fully RE system configurations are not financially viable in the Maldives while the RE-diesel hybrid systems could bring down the price of electricity with 5-10 $cent/kWh in smaller outer islands. Assuming that these latter systems with a high probability of adoption are implemented, the results show that 10% of the electricity in the Maldives could be supplied by RE based systems in a cost effective way.