The impact of rate design and net metering on the bill savings from distributed PV for residential customers in California

Net metering has become a widespread mechanism in the U.S. for supporting customer adoption of distributed photovoltaics (PV), but has faced challenges as PV installations grow to a larger share of generation in a number of states. This paper examines the value of the bill savings that customers receive under net metering, and the associated role of retail rate design, based on a sample of approximately two hundred residential customers of California's two largest electric utilities. We find that the bill savings per kWh of PV electricity generated varies by more than a factor of four across the customers in the sample, which is largely attributable to the inclining block structure of the utilities' residential retail rates. We also compare the bill savings under net metering to that received under three potential alternative compensation mechanisms, based on California's Market Price Referent (MPR). We find that net metering provides significantly greater bill savings than a full MPR-based feed-in tariff, but only modestly greater savings than alternative mechanisms under which hourly or monthly net excess generation is compensated at the MPR rate.     

Research on energy storage capacity configuration for PV power plants using uncertainty analysis and its applications

Compensating for photovoltaic (PV) power forecast errors is an important function of energy storage systems. As PV power outputs have strong random fluctuations and uncertainty, it is difficult to satisfy the grid-connection requirements using fixed energy storage capacity configuration methods. In this paper, a method of configuring energy storage capacity is proposed based on the uncertainty of PV power generation. A k-means clustering algorithm is used to classify weather types based on differences in solar irradiance. The power forecast errors in different weather types are analyzed, and an energy storage system is used to compensate for the errors. The kernel density estimation is used to fit the distributions of the daily maximum power and maximum capacity requirements of the energy storage system; the power and capacity of the energy storage unit are calculated at different confidence levels. The optimized energy storage configuration of a PV plant is presented according to the calculated degrees of power and capacity satisfaction. The proposed method was validated using actual operating data from a PV power station. The results indicated that the required energy storage can be significantly reduced while compensating for power forecast errors.     

Social norms,trust and control of power theft in Uganda: Does bulk metering work for MSEs?

Power theft is still rampant in many developing countries. Governments and utility providers tend to favor technical solutions, neglecting the socio-economic dimension. This article analyzes the interaction between the socio-economic factors trust, informal social norms, awareness and electricity pricing effect and technical control measures in Uganda. After reforming its power sector, Uganda introduced two technical innovations: bulk metering for micro and small enterprises (MSE) and prepaid metering for households. The bulk metering system imposes a strong form of social control among MSEs. Drawing on semi-structured interviews with 29 MSEs and 16 experts in Uganda, this article shows how well bulk metering works in practice. It finds that trust is key in the relations between electricity user and utility provider, between citizens and government overseeing the energy sector as well as within bulk metering groups of MSEs. The electricity price impacts MSEs' ability to pay and to some extent also their willingness to pay. Finally, power theft used to be accepted as an informal social norm. Change is happening, but is currently undermined by corruption and patronage networks in the energy sector and the political system, impacting people's attitude to compliance – regardless of the privatization of the electricity sector.     

Validation of the Sandia model with indoor and outdoor measurements for semi-transparent amorphous silicon PV modules

This paper presents a set of indoor and outdoor measurement methods and procedures to determine the empirical coefficients of the Sandia Array Performance Model (SAPM) for a semi-transparent amorphous silicon (a-Si) PV module. After determining and inputting the total 39 parameters into the SAPM, the dynamic power output of the a-Si PV module was predicted. In order to validate the accuracy of using SAPM for simulating the energy output of the a-Si PV module, a long-term outdoor testing campaign was conducted. The results indicated that the SAPM with indoor and outdoor measured coefficients could accurately simulate the energy output of the a-Si PV module on sunny days, but it didn't work well on overcast days due to the inappropriate spectral correction as well as the equipment measuring error caused by the intense fluctuation of solar irradiance on overcast days. Specifically, all the errors between the simulated daily energy output and the measured one were less than 4% on sunny days. In order to achieve a better prediction performance for a-Si PV technologies, the SAPM was suggested to incorporate a more comprehensive spectral correction function to correct the impact of solar spectrum on overcast days in future.     

中国西部离网光伏、风力发电系统优化配置与补贴测算工具

介绍了关于用可再生能源实现中国西部农村地区电气化工程的一个项目.项目开发了一个为离网光伏、风力发电系统的设计和基于成本的电价以及投资提供指导的便捷工具,解决系统优化配置与成本评估标准的问题,以实现离网系统运营成本全网分摊的合理计算,使西部农村可再生能源发电项目实现可持续发展.描述了此系统优化配置与补贴测算工具所采用的方法,以及该工具的操作步骤,阐明了此工具将在未来实施的偏远农村可再生能源供电系统项目中发挥的作用.     

Comparative performance analysis of a grid connected PV system for hydrogen production using PEM water,methanol and hybrid sulfur electrolysis

This paper presents comparative performance analysis of photovoltaic (PV) hydrogen production using water, methanol and hybrid sulfur (SO₂) electrolysis processes. Proton exchange membrane (PEM) electrolysers are powered by grid connected PV system. In this system design, electrical grid is considered as a virtual energy storage system (VESS) where the surplus of PV production can be injected and subsequently taken to support the electrolyser. Methanol (ME) and hybrid sulfur (HSE) electrolysis are compared to the conventional water electrolysis (WE) in term of operating cell voltage. Based on the experimental results reported in the literature, semi-empirical models describing the relationship between the hydrogen production rate and the electrolyser cell power input are proposed. Furthermore, power and hydrogen management strategy (PHMS) is developed. Case study is carried out to show the impact of each type of electrolysis on the system component sizes and evaluate the hydrogen production potentialities. Results show that the use of ME allows to produce 65% more hydrogen than with using WE. Moreover, the amount of hydrogen produced is almost double in the case of HSE. At Algiers city, based on a grid connected PV/Electrolyser system, it is possible to produce about 25 g/m² d and 29 g/m² d of hydrogen, respectively, through ME and HSE compared to 15 g/m² d of hydrogen when using WE.     

Real‐time wind field reconstruction from LiDAR measurements using a dynamic wind model and state estimation

The use of light detection and ranging (LiDAR) instruments offer many potential benefits to the wind energy industry. Although much effort has been invested in developing such instruments, the fact remains that they provide limited spatio‐temporal velocity measurements of the wind field. Moreover, LiDAR measurements only provide the radial (line‐of‐sight) velocity component of the wind, making it difficult to precisely determine wind magnitude and direction, owing to the so‐called ‘cyclops’ dilemma. Motivated by a desire to extract more information from typical LiDAR data, this paper aims to show that it is possible to accurately estimate, in a real‐time fashion, the radial and tangential velocity components of the wind field. We show how such reconstructions can be generated through the synthesis of an unscented Kalman filter that employs a low‐order dynamic model of the wind to estimate the unmeasured velocities within the wind field, using repeated measurement updates from typical nacelle‐mounted LiDAR instruments. This approach is validated upon synthetic data generated from large eddy simulations of the atmospheric boundary layer. The accuracy of the wind field estimates are validated across a variety of beam configurations, look directions, atmospheric stabilities and imperfect measurement conditions. The main outcome of this paper is a technique that offers the potential to accurately reconstruct wind fields from LiDAR data, overcoming the cyclops dilemma in the process. The ultimate aim of this research is to provide reliable gust detection warning systems to offshore construction workers, in addition to accurate wind field estimates for use in preview turbine pitch control systems. © 2014 The Authors. Wind Energy published by John Wiley & Sons Ltd.     

Design,modelling and optimal power and hydrogen management strategy of an off grid PV system for hydrogen production using methanol electrolysis

Hydrogen used as an energy carrier and chemical element can be produced by several processes such as gasification of coal and biomass, steam reforming of fossil fuel and electrolysis of water. Each of these methods has its own advantage and disadvantage. Electrolysis process is seen as the best option for quick hydrogen production. Hydrogen generation by methanol electrolysis process (MEP) gained much attention since it guarantees high purity gas and can be compatible with renewable energies. Furthermore, due to its very low theoretical potential (0.02 V), MEP can save more than 65% of electrical energy required to produce 1 kg of hydrogen compared to water electrolysis process (WEP). Electrolytic hydrogen production using solar photovoltaic (PV) energy is positioned to become as one of the preferred options due to the harmful environmental impacts of widely used methane steam reforming process and also since the prices of PV modules are more competitive.In this paper, hydrogen production by MEP using PV energy is investigated. A design of an off grid PV/battery/MethElec system is proposed. Mathematical models of each component of the system are presented. Semi-empirical relationship between hydrogen production rate and power consumption at 80 °C and 4 M concentration is developed. Optimal power and hydrogen management strategy (PHMS) is designed to achieve high system efficiency and safe operation. Case studies are carried out on two tilts of PV array: horizontal and tilted at 36° using measured meteorological data of solar irradiation and ambient temperature of Algiers site. Simulation results reveal great opportunities of hydrogen production using MEP compared to the WEP with 22.36 g/m² d and 24.38 g/m² d of hydrogen when using system with horizontal and tilted PV array position, respectively.