Search

• Zero net energy is feasible when clean fuel is combined with electrification. • Building energy consumption valuation method impacts the component sizing. • Time dependent valuation of energy in California reflects its cost and emissions. • Solid oxide fuel cell provides efficient electricity and heat at the building. • Building can go off-grid with optimized operation of battery and fuel cell. California is seeking to mandate Zero Net Energy (ZNE) buildings by 2030 as part of its efforts to combat climate change. A ZNE building is required to compensate its annual energy consumption from the grid (electricity or gas) by injecting clean electricity back to the grid. So far, the most common approach for a ZNE building is utilizing solar photovoltaic (PV) or a PV and battery energy storage system. One key problem is the feasibility of installing PV if the surface area requirement is too large to achieve ZNE; another issue is grid congestion during the off-peak hours of midday when a large number of houses export their excess solar power to the grid. Hence, other ZNE home scenarios need to be evaluated to tackle these restrictions in achieving California's climate goals. In this work, we proposed and evaluated different system arrangements to reduce the required PV installation that is commonly installed as power generation source for ZNE residential units in California. The aim of this technical analysis is to provide a societal level policy guidance to accelerate fulfilling the ZNE home mandate. Due to the availability of the gas grid and potential for having more renewable gas in the grid, we investigated using gas-based heat generation versus only electric-based heat appliances. In addition, we incorporated a residential solid oxide fuel cell (SOFC) on the building site as a micro combined heat and power (mCHP) to facilitate achieving ZNE. The impact and contributions of different components, including energy storage, on grid-dependence, and the overall energy demand are also studied. With analysis of different mix of technologies that could be used for a ZNE home, we propose the potential solutions and discuss their strengths and weakness. In this paper, energy performance and optimal PV capacity are assessed for a ZNE home in all 16 climate zones of California established by California Energy Commission (CEC). The ZNE measurements for all four scenarios are based on three metrics of energy evaluation: (1) site energy (energy measured by the meter used at the building site); (2) source energy (raw fuel consumption at the source of energy generation to account for energy loss in production and distribution); and (3) time dependent valuation (TDV) of energy, which has been developed by the CEC to comply with its building energy efficiency standards. The TDV of each energy type depends on the time of use, climate, grid constraints, and other factors that reflect its societal value at any given hour of the year. The PV size required by each ZNE metric is calculated and compared. The results proved that relying on some gas in addition to electricity improves the practicality of required PV for ZNE homes particularly in regions with high heating demands. It was found that depending on the energy metric (site, source, and TDV), a different arrangement is required for the most efficient ZNE performance. Unlike the site metric, using source and TDV metrics where electricity is more valuable than gas shows that having both gas and electricity significantly reduces the PV size. This encourages investment in introduction of more renewable gas in the grid as one possible solution to achieving ZNE in individual homes. The great impact of an mCHP SOFC on a ZNE home in terms of reliability and feasibility points to the need for research, development, and commercialization to reduce the cost of mCHP SOFCs in residential application. Also, the addition of a battery does not reduce the PV size with site and source metrics; it only reduces the electric grid reliance. However, with TDV, where the time of energy consumption affects its value, not only does it reduce grid reliance during peak hours, but also less PV is required to achieve ZNE. [ABSTRACT FROM AUTHOR]

California is a pioneer in energy system innovations, and it is not surprising that the state is leading the nation in the adoption of microgrids. However, the inherent characteristics of microgrids make them challenging to integrate and operate within the current energy system. This is mainly because unlike other decentralized energy systems, microgrids often tend to interact with the centralized grid infrastructure as both a parallel and a competing distribution grid model at the micro scale. The adoption and integration of microgrids, therefore, represents a socio-technical transition in the electric power sector. In this context, this study relies on the Multi-Level Perspective framework to examine the drivers, contexts, processes, and policies that have enabled an ongoing transition in California's electricity system that has allowed adoption of microgrids. The analysis shows that even though several drivers carry weight, including resilience concerns and market factors, California's pathway to microgrids is largely driven by the legislative and regulatory push toward clean energy and a symbiotic relationship between powerful regime actors and a microgrid niche. This is enabling a transformation in the state's energy system, in which the entry of microgrids is subtly facilitated by the regime in a way that does not threaten the current utility-dominated electricity system. By providing a detailed account of how a decentralized energy system that challenges the centralized grid regime has made its place in the centralized grid regime in California, this paper identifies the key facets that affect the integration of microgrids in the broader context of energy transitions. • A Multi-Level Perspective analysis of microgrid adoption in California is presented. • Legislative and regulatory push toward clean energy is driving this transition. • Microgrids are being nurtured by a symbiotic relationship between regime and niche. • The study shows that symbiotic niche-regime relationship is key in energy transitions. [ABSTRACT FROM AUTHOR]