Storage Optimal Control under Net Metering Policies

Electricity prices and the end user net load vary with time. Electricity consumers equipped with energy storage devices can perform energy arbitrage, i.e., buy when energy is cheap or when there is a deficit of energy, and sell it when it is expensive or in excess, taking into account future variations in price and net load. Net metering policies indicate that many of the utilities apply a {customer selling} rate lower than or equal to the retail {customer buying rate} in order to compensate excess energy generated by end users. In this paper, we formulate the optimal control problem for an end user energy storage device in presence of net metering. We propose a computationally efficient algorithm, with worst case run time complexity of quadratic in terms of number of samples in lookahead horizon, that computes the optimal energy ramping rates in a time horizon. The proposed algorithm exploits the problem's piecewise linear structure and convexity properties for the \textit{discretization} of optimal Lagrange multipliers. The solution has a \textit{threshold-based structure} in which optimal control decisions are independent of past or future price as well as of net load values beyond a certain time horizon, defined as a \textit{sub-horizon}. Numerical results show the effectiveness of the proposed model and algorithm. Furthermore, we investigate the impact of forecasting errors on the proposed technique. We consider an Auto-Regressive Moving Average (ARMA) based forecasting of net load together with the Model Predictive Control (MPC). We numerically show that adaptive forecasting and MPC significantly mitigate the effects of forecast error on energy arbitrage gains

Closing the California Clean Energy Divide: Reducing Electric Bills in Affordable Multifamily Rental Housing with Solar+storage

This economic analysis indicates that pairing solar PV with battery storage systems can deliver significant electricity bill savings for California affordable housing residents and property owners.Battery storage is emerging as an effective new strategy for reducing electricity costs for affordable multifamily rental housing in California. Battery storage systems not only provide economic returns today, they can also preserve the value of solar in an evolving policy and regulatory environment. Because batteries empower owners of solar photovoltaic (PV) systems to take control of the energy they produce and when they consume it, storage can deliver deeper cost reductions that can be shared among affordable housing owners, developers, and tenants.California has installed numerous integrated solar and battery storage projects; however, few have served lowincome tenants or owners of affordable rental housing. This disparity is due to many factors, including a lack of information about the economics of these systems in multifamily housing. To provide that needed information, Clean Energy Group, California Housing Partnership, and Center for Sustainable Energy, with analytical support from Geli, are embarking on a series of reports on solar and storage in California affordable multifamily rental housing.This first report examines the utility bill impacts of adding battery storage to stand-alone solar in affordable rental housing facilities in California's three investor-owned utility service territories, each with different rate structures. It is the first such report ever completed on these technologies in this sector in California.The report reaches several key conclusions:Under current utility rate tariffs, the combination of solar and storage technologies could virtually eliminate electric bills for many owners of affordable housing properties. Unlike stand-alone solar, which reduces energy consumption expenses but does little to offset demand related charges, a properly sized solar and battery storage system can eliminate nearly all electricity expenses, resulting in an annual electric utility bill of less than a few hundred dollars in some cases.It makes good economic sense today for solar and battery storage to be installed in affordable multifamily rental housing in California. The addition of battery storage to solar improves the economics of each property analyzed across all utility territories, reducing project payback by over three years in some cases.The addition of storage technologies has the potential to nearly double stand-alone solar electricity bill savings at about a third of the cost of solar. For example, the addition of a $112,100 battery storage system to a$385,000 solar installation increased savings from $15,000 per year to$27,900, an 85 percent increase in savings for only a 29 percent increase in cost

A review of microgrid development in the United States – A decade of progress on policies, demonstrations, controls, and software tools

Microgrids have become increasingly popular in the United States. Supported by favorable federal and local policies, microgrid projects can provide greater energy stability and resilience within a project site or community. This paper reviews major federal, state, and utility-level policies driving microgrid development in the United States. Representative U.S. demonstration projects are selected and their technical characteristics and non-technical features are introduced. The paper discusses trends in the technology development of microgrid systems as well as microgrid control methods and interactions within the electricity market. Software tools for microgrid design, planning, and performance analysis are illustrated with each tool's core capability. Finally, the paper summarizes the successes and lessons learned during the recent expansion of the U.S. microgrid industry that may serve as a reference for other countries developing their own microgrid industries

DESIGN OF CONSUMMER THERMAL SUBSTATIONS FOR THE INTEGRATION OF DISTRIBUTED SOLAR TECHNOLOGIES IN DISTRICT HEATING SYSTEMS

In most cases, building service designers choose between Solar thermal (ST) and District Heating (DH) technologies for their integration in buildings. By doing so, only a fraction of the buildings within a particular district is used for ST, while at the same time energy intensity in DH networks can be reduced. In some cases, building-integrated solar thermal systems are connected to DH networks by means of dedicated pipes. In all these cases, sub-optimal situations are reached with lower fraction of renewable heat, reduced network strength and/or additional heat losses. In this paper, a consummer substation concept is proposed with reversible heat flow and net metering, which avoids local thermal storage in the solar loop. Adaptations required for multi-dwelling buildings are presented.European Commission's H2020, 768567, RELaTE

Unintended Effects of Residential Energy Storage on Emissions from the Electric Power System.

In many jurisdictions, policy-makers are seeking to decentralize the electric power system while also promoting deep reductions in the emission of greenhouse gases (GHG). We examine the potential roles for residential energy storage (RES), a technology thought to be at the epicenter of these twin revolutions. We model the impact of grid-connected RES operation on electricity costs and GHG emissions for households in 16 of the largest U.S. utility service territories under 3 plausible operational modes. Regardless of operation mode, RES mostly increases emissions when users seek to minimize their electricity cost. When operated with the goal of minimizing emissions, RES can reduce average household emissions by 2.2-6.4%, implying a cost equivalent of $180 to$5160 per metric ton of carbon dioxide avoided. While RES is costly compared with many other emission-control measures, tariffs that internalize the social cost of carbon would reduce emissions by 0.1-5.9% relative to cost-minimizing operation. Policy-makers should be careful about assuming that decentralization will clean the electric power system, especially if it proceeds without carbon-mindful tariff reforms

Microgrids & District Energy: Pathways To Sustainable Urban Development

A microgrid is an energy system specifically designed to meet some of the energy needs of a group of buildings, a campus, or an entire community. It can include local facilities that generate electricity, heating, and/or cooling; store energy; distribute the energy generated; and manage energy consumption intelligently and in real time. Microgrids enable economies of scale that facilitate local production of energy in ways that can advance cost reduction, sustainability, economic development, and resilience goals. As they often involve multiple stakeholders, and may encompass numerous distinct property boundaries, municipal involvement is often a key factor for successful implementation. This report provides an introduction to microgrid concepts, identifies the benefits and most common road blocks to implementation, and discusses proactive steps municipalities can take to advance economically viable and environmentally superior microgrids. It also offers advocacy suggestions for municipal leaders and officials to pursue at the state and regional level. The contents are targeted to municipal government staff but anyone looking for introductory material on microgrids should find it useful

Air Emissions of Ammonia and Methane from Livestock Operations: Valuation and Policy Options

The animal husbandry industry is a major emitter of methane, which is an important greenhouse gas. The industry is also a major emitter of ammonia, which is a precursor of fine particulate matter—arguably, the number-one environment-related public health threat facing the nation. We present an integrated process model of the engineering economics of technologies to reduce methane and ammonia emissions at dairy operations in California. Three policy options are explored: greenhouse gas offset credits for methane control, particulate matter offset credits for ammonia control, and expanded net metering policies to provide revenue for the sale of electricity generated from captured methane gas. Individually, any of these policies appears to be sufficient to provide the economic incentive for farm operators to reduce emissions. We report on initial steps to fully develop the integrated process model that will provide guidance for policymakers.methane, ammonia, carbon dioxide, greenhouse gases, climate change, offset, particulate matter, net metering, environmental policy, CAFO, manure management, biodigester, electricity, global warming, cost-benefit, incentive approach