Energy self-sufficient households with photovoltaics and electric vehicles are feasible in temperate climate

Table 1. Overview of key past studies on residential energy self-sufficiency [10–19]. Source Aim and methods Results Differences to our study GROSSPIETSCH, Thommes (10) Simulation model which shows how, when, and where a self-sufficient neighborhood is economically feasible. How: Through solar PV together with a battery system (1) or together with batteries and hydrogen storage (2). When: Costs have to decrease 21% (1) and 51% (2), respectively, to be competitive to households relying on fossil fuels. Where: Little seasonality (1) to high seasonality (2). • No timeframe • Ranging from low to high latitudes • Neighborhood containing a community of households of different sizes and an office building • No sensitivity analysis of factors • Technically not feasible with current efficiencies • No consideration of electric mobility Murray, Orehounig (11) The potential of long-term and short-term storage systems are modelled in a decentralized neighborhood with minimizing costs and CO2- emissions. Three scenarios are created and modelled until 2050. The model is tested on two sample municipalities in Switzerland. Modelled data regarding technologies and price developments until 2050. Development in the locations of Zernez and Altstetten, Switzerland, are presented. Furthermore, the importance of retrofitting the current building stock is mentioned because of the limitation of renewable energy. • No information about single buildings is given • Focus on the two case study locations • Local gas, electricity, and heating grid are present and used • No consideration of electric

mobility Zhang, Campana (12) Grid-connected PV-hydrogen/battery systems are investigated with the creation of three strategies for the hydrogen storage. Moreover, a high and a low- cost scenario are created. Strategies to produce and store hydrogen are dependent on the electricity price and make sense when a seasonal mismatch between load and PV production occurs. Hydrogen storage shows a better performance when grid power fluctuation is considered. • Connected to the grid • No clear relation to the residential sector • No information about sizing the hydrogen or battery system Weniger, Tjaden (13) Optimal sizing of PV-battery-systems in the residential sector are analyzed. In addition, a sensitivity analysis is conducted regarding PV and battery size in different cost scenarios. The absolute yield and the PV generator orientation will be of small relevance in the future. The most optimal PV sizes are reached in small-scale systems with high self-consumption rates and degree of self- sufficiency (above 70%). In a long-term perspective, PV systems with batteries will be the most economical solution. • Connected to the grid • Special case (single-family building) located in Lindenberg, Germany • Information about the household is restricted to its electricity demand of 4 MWh/year • No renewable heating system is considered • No hydrogen production is considered • Feed-in tariff is applied in the modelling • No consideration of electric mobility Good, Andresen (14) Solar energy solutions are modelled and compared with the aim of fulfilling the requirements of a net

zero energy balance. If the building only uses solar PV, the net zero energy balance shows the better performance than using solar thermal collectors in combination with PV or using the technology of hybrid photovoltaic-thermal modules. • Special case of a single-family building in Norway • Connected to the grid • No storage of electricity • No consideration of electric mobility Milan, Bojesen (15) A model is developed to optimally size a 100% renewable supply system while considering overall costs. It is applied on a case study in Denmark. The requirement of a net zero-energy building is successfully applied and optimally if the PV system is combined with a heat pump. Available rooftop area is not used for solar thermal collectors. • Connected to the grid • Special case with conditions of Northern Denmark • No hydrogen production is considered • No consideration of electric mobility Maroufmashat, Fowler (16) A generic mathematical model is developed to manage future communities which use hydrogen as an energy carrier. The model is applied to a case study consisting of four energy hubs which work together. Results are based on a case study located in Ontario, Canada. Annual total emissions and the levelized costs of hydrogen of the energy hub networks are presented. To produce hydrogen on-site is more economical than purchase it. The environmental advantages of hydrogen vehicles are assessed in addition. • Focus on hydrogen production only • A network of energy hubs is investigated with no further explanation of their composition • No detailed information about

the residential sector • No storage of electricity in batteries • Consideration of hydrogen fueled cars (Continued) Energy self-sufficient households with photovoltaics and electric vehicles are feasible in temperate climate PLOS ONE | https://doi.org/10.1371/journal.pone.0227368 March 4, 2020 3 / 25