Small Renewable Energy Research Articles

Reviewing the Situation and Prospects for Developing Small Renewable Energy Systems in Poland

The objective of this study was to evaluate changes in the number of small renewable energy sources (RES) power plants and the volume of generated energy in the years 2016–2020, with an outlook to year 2025. The study covered the area of Poland, including the division into provinces and different sources of renewable energy. Absolute values of electric power production and sale were presented, in addition to calculated structure indices. Moreover, the number and structure of small power plants using different renewable energy sources was determined for every Polish province. A classification of the provinces was made, where four classes were distinguished depending on the number of RES plants operating in the provinces. The research results allowed us to diagnose the current situation and make a prognosis for the future, which may translate into support for the development of particular types of installations, depending on the natural and economic characteristics of each area. The added value of the study stems from the fact that previous reports focused mainly on micro or large power plants and the time span covered data before and during the pandemic. This made it possible to assess the impact of the pandemic on the development of small renewable energy sources.

Low-Cost Communication Interface between a Smart Meter and a Smart Inverter

The need for a low-cost interface between the grid and small (<250 kW) renewable distributed energy resources (DERs) is growing in importance as the number of small DERs continues to grow. In this study, a system architecture was proposed to investigate paths to an affordable interconnection for small renewable DERs.Then, a low-cost communication interface between a smart meter and smart inverter was installed using a commercially available bridge device. The interface device was selected based on an assessment concluding that it would be able to support the emerging advanced metering infrastructure (AMI) network. Next, messages were passed across the experimental end-to-end communication interface to test their speed and reliability. Success was based on whether the key functions defined in the standard IEEE 2030.5 were executed or not, which include set points, disconnect/reconnect, and Volt-VAr optimization. The results of the testing provided detailed insights into the benefits and limitations of the proposed architecture. Intermittency of weather-dependent DERs (e.g., solar and wind) adversely impacts the power quality of a DER, making hourly day-ahead prediction nearly impossible. With this in mind, the investigation also considered the potential of using smart inverter functions to reduce DER’s intermittency.

Lifetime Maximization in Underwater Wireless Communication Networks

The rise in demand for underwater wireless communication networks (UWCN) has been driven by the emergence of new applications including unmanned underwater vehicles, deep-sea exploration, maritime and underwater archaeology research, and diver communications. For various applications, underwater network lifetime must be long, since unlike terrestrial sensor networks, it is a major job to change/recharge node batteries in underwater environments. In this paper, we introduce a solution where critical nodes in a UWCN are periodically recharged by small renewable energy sources. Further, a caching mechanism is introduced to relieve critical nodes of heavy workload when their residual energies run low. By leveraging these two techniques of energy replenishment and content-caching, the network lifetime extension challenge is formulated as an optimization problem. The results indicate that our proposed solution offers up to 45% longer UWCN lifetime compared to existing solutions.

Forecasting of Power Quality Parameters Based on Meteorological Data in Small-Scale Household Off-Grid Systems

Off-grid power systems are often used to supply electricity to remote households, cottages, or small industries, comprising small renewable energy systems, typically a photovoltaic plant whose energy supply is stochastic in nature, without electricity distributions. This approach is economically viable and conforms to the requirements of the European Green Deal and the Fit for 55 package. Furthermore, these systems are associated with a lower short circuit power as compared with distribution grid traditional power plants. The power quality parameters (PQPs) of such small-scale off-grid systems are largely determined by the inverter’s ability to handle the impact of a device; however, this makes it difficult to accurately forecast the PQPs. To address this issue, this work compared prediction models for the PQPs as a function of the meteorological conditions regarding the off-grid systems for small-scale households in Central Europe. To this end, seven models—the artificial neural network (ANN), linear regression (LR), interaction linear regression (ILR), quadratic linear regression (QLR), pure quadratic linear regression (PQLR), the bagging decision tree (DT), and the boosting DT—were considered for forecasting four PQPs: frequency, the amplitude of the voltage, total harmonic distortion of the voltage (THDu), and current (THDi). The computation times of these forecasting models and their accuracies were also compared. Each forecasting model was used to forecast the PQPs for three sunny days in August. As a result of the study, the most accurate methods for forecasting are DTs. The ANN requires the longest computational time, and conversely, the LR takes the shortest computational time. Notably, this work aimed to predict poor PQPs that could cause all the equipment in off-grid systems to respond in advance to disturbances. This study is expected to be beneficial for the off-grid systems of small households and the substations included in existing smart grids.

The Road to Clean Energy: And a Changing of the Guard [Editors’ Voice

No one ever said a clean energy transformation would be easy. The history behind establishing and expanding reliable electric power systems based on networked, large, central generation is engrained in operations and planning processes as well as the institutions and personnel that support them. A variety of large and small renewable energy sources have been entering the picture and displacing environmentally challenged resources. As the speed of change accelerates in various regions, traditional system management paradigms bend and creak to accommodate the trends.

Hydropower: renewable and contributing to sustainable development? A critical analysis from the Mazar-Dudas project (Ecuador)

ABSTRACT The energy transition has provided a framework for designing and implementing renewable energy policies in a growing number of countries in recent years. The discourse from both international energy organisations and national governments around these renewable energy policies highlights its -supposed- sustainable nature. However, much evidence shows that the “renewable” component of these energy policies and the impact on local communities’ sustainable development are much smaller than what is claimed in their discourse. This paper analyses the Mazar-Dudas hydropower project (Ecuador) case study, which is officially classified as a small renewable energy project (21 MW) with presumable low environmental impact and significant positive effects on sustainability of local communities. Although, the sustainability associated with hydropower production is one of the most controversial aspects of this energy production technology. Based on interviews with relevant actors and the subsequent thematic content analysis, the results highlight that the environmental impact is perceived as significant, contrary to what it is said in the official discourse. Additionally, the benefit-sharing scheme's effects of this hydropower project are far below expectations.

Transition of renewable energy policies in Malaysia: Benchmarking with data envelopment analysis

Using data envelopment analysis (DEA) and Malmquist index (MI) method, this study investigates the effect of the transition of renewable energy operational policies in Malaysia through static and dynamic analyses. This study also evaluates the performance of the country's operational policies in the development of renewable energy including small renewable energy power (SREP), feed-in tariff (FiT), large-scale solar photovoltaic (LSSPV) and net energy metering. In this study, three inputs (employment, electricity generation and renewable energy licensed capacity) and two outputs (gross domestic product and renewable energy generation) are used. Using the panel dataset, this study applies the Malmquist productivity index to calculate the changes in efficiency, technology and total productivity in four Malaysian regions in 2010–2017. Results show that the East Malaysia region is the most efficient in developing renewable energy during the aforementioned period. Results also demonstrate that Malaysia experienced a decrease in renewable energy efficiency during the first policy transition from the SREP programme to the FiT programme, and efficiency increased during the second policy transition from the FiT programme to the integrated programme in 2017. Malaysia's renewable energy policy transition has also contributed up to sevenfold of social benefits in solar photovoltaic industry job creations between 2012 and 2019, and up to 0.16% in carbon emission reduction of environmental impacts from 2012 to 2018. Using DEA and the MI method, this study highlights the phase of transition of renewable energy policies and the effect of implementing these policies on renewable energy development in Malaysia.

Development of a hybrid concentrated solar‐natural gas system

This work aims to design a small (5 kW) renewable energy plant, which can supply fully dispatchable electricity to the grid at a cost, inclusive of dispatchability, better than using wind or solar photovoltaic and batteries, specific for remote areas where the solar irradiance is significant, but plagued by clouds. A beam down point concentrator is coupled to a two-tank thermal energy storage system and natural gas heater, to produce constant power by using a Stirling engine. Considered as a conventional combustion fuel plant, the fuel conversion efficiency on the typical day of every month of the typical year is 82%-222%, an average of 124%. This means that replacing an oil generator with the proposed device would permit an 83% reduction of CO2 emissions.

Small Renewable Energy Community: The Role of Energy and Environmental Indicators for Power Grid

The Clean Energy for all Europeans Package pushes for the diffusion of renewable energy communities, introducing their definition in the European legislative framework. Following this interest, this paper analyses the energy and environmental performance of a renewable energy community composed of two office buildings located in Naples (Italy). Each building has a rooftop photovoltaic plant and one office presents an electric vehicle. The heating and cooling demands of both offices are satisfied by two reversible air to water heat pumps. The offices are connected through an electric microgrid and they are in parallel with a power grid. Buildings and plants are modelled and simulated by means of TRNSYS 17 simulation software. The first analysis has concerned the comparison of the results achieved in renewable energy community configuration and from individual buildings in terms of quantity of electricity imported, exported from/to power grid and consumed on-site. The share of self-consumed photovoltaic electricity rises up to 79% when energy sharing is allowed. The second analysis has been carried out to evaluate the energy and environmental performance of a renewable energy community by means of fixed and hourly varying values for power grid efficiency and emission factors for electricity. The use of time-dependent indicators has led to a lower community primary energy demand and carbon dioxide emissions of 18% and 12%, respectively, in comparison with the scenario in which the fixed parameters have been adopted.

Tightening the Legal ‘Net’: The Constitution’s Supremacy Clause Straddle of the Power Divide

This article analyzes Constitutional Supremacy Clause tensions in preempting state law that addresses climate change and the rapid warming of the Planet. Net metering laws, enacted in 80% of U.S. states, are a primary legal mechanism to control and mitigate climate warming. This article analyzes three recent federal court decisions creating a preemptive Supremacy Clause stand-off between federal and state law and presents a detailed state-by-state analysis of which those 80% of states’ laws could be preempted by legal challenge. If state net metering laws affected only ordinary technologies, this issue would not be front and center with global warming. However, state net metering laws are the most widely deployed U.S. incentive for renewable energy to address climate warming. This article examines and documents, state-by-state, that 75% of the states with questionable legal practices a decade ago have changed their laws to avoid legal prohibitions, while some others have not. At the federal level, the federal government recently revised regulations substantially restricted four decades of federal regulatory incentives for small renewable energy projects pursuant to the key statute that President Jimmy Carter characterized as the federal response to fight the “moral equivalent of war!” In its conclusion, this article provides a legal path for states to insulate their state laws from Constitutional challenge while still effectively addressing climate change. There is much at risk in the legal structure of U.S. state net metering laws, as world climate approaches the tipping points that will alter regional and global environmental balances irreversible within the time span of our current civilization.

Properties Analysis of Dual IPCs 240 with Three Branches Case Study in an Energy Transmission Line Connected to a Hydroelectric Mini-Power Plant

In this paper, the newly developed “Dual Interphase Power Controller (IPC) 240” technology is used to increase the reliability of transmission lines for small renewable energy plants. This asymmetric compensation method based on symmetrical components has used two IPC. The first one is placed at the sending end of the line and the second IPC at the receiving end of the line. During normal operation of the transmission line formed, the electrical service continuity is ensured at the load using reactances, which adjust according to the power angle. When a permanent single-phase fault occurs, triggering the circuit breakers of the infected phase, the two IPCs are reconfigured so that the first performs a three-phase / two-phase transformation and the second a two-phase/three-phase transformation of voltage to continue providing a sufficient power for the load. Data from a power transmission line (30 kV-5 MW) from a mini hydroelectric power station has been used in a virtual network under Matlab/Simulink to test the functions dedicated to this technology. The results of the tests obtained and presented show the feasibility of this technology. The efficiency is also guaranteed because the electricity service is 100% assured in the absence of contingency and almost 70% during the contingency of the single-phase short-circuit type.

Computer Simulation of MPPT Converter to Control PV Panel-Battery System

This research intends to build and simulate a small renewable energy system consists of PV panel, lead-acid battery, and bidirectional DC-DC converter. Bidirectional Buck-Boost converter was used to regulating the voltage and current coming from the solar panels going to the battery and vice versa. It operates a Buck converter which charges the battery from the PV panel when State of charge (SOC) reaches less than 0.4. The battery needs 100 ms to charge from 12.2 V to 13 V with duty cycle 0.5 and 1 A. Also work as a Boost converter when SOC reaches 1 the battery was discharge for 100 ms and SOC decreases from 1 to 0.4.A PSPICE PV panel model (consists of 20 solar cells, 12 V and 60 W maximum power at 25 °C with 1000 W/m2 solar irradiation) has been used as a source of energy to the power circuit. The output of PV panel relates to Boost converter, which is the key for changing the PV’s terminal voltage to track the maximum power, it was rising a PV panel voltage from 10 V to 22 V for all variation of surface temperature from 300 K to 350 K at frequency 10 kHz and ΔVo = 1.1 V.

Optimal peer-to-peer energy management between grid-connected prosumers with battery storage and photovoltaic systems

• An optimal P2P energy sharing for grid-connected prosumers is modelled. • The prosumers use stationary, dual-tracking PV systems and battery storage system. • Prosumers have P2P bidirectional energy trading with each other. • Lifecycle cost and break-even analyses are conducted for the prosumers in the P2P. • Results demonstrate cost savings for prosumers operating with the optimal P2P model. This paper proposes a model for the optimal Peer-to-Peer energy sharing of grid-connected Prosumers. Current models within available literature do not include the constraint which forbid small renewable energy producers to share their excess power through the national grids; this leads to prosumers dissipating their excess power generated or using costly energy storage systems. Additionally, most of these models look at the savings made by the Peer-to-Peer community, without computing the cost reduction or benefit of each prosumer taken individually. Thus, these models are not suitable or directly applicable to many countries such as South Africa. For these reasons, the main aim of this paper is to develop a Peer-to-Peer energy sharing model that considers the above mentioned gaps. The proposed system consists of two prosumers; a residential prosumer that employs a roof mounted photovoltaic system with energy storage capabilities, and commercial prosumer with a dual-tracking photovoltaic system. The prosumers are connected to each other by power lines for P2P operation. The developed model minimizes both prosumers’ operation costs by maximizing the use of the power from the renewable energy sources; optimally managing the internal power sharing between the prosumers; and minimizing the use of the electrical utility operating with the Time-of-Use rate. The study uses the dissimilarity and complementarity of the load patterns in the South African residential and commercial energy sectors as an asset to implement the Peer-to-Peer energy sharing between the prosumers operating in these two sectors. Using a case study in South Africa, the results have demonstrated that, as compare to using the grid as sole power source, the residential prosumer can achieve a total daily cost reduction of 62.71% in summer and 68.99% in winter; while the commercial can achieve 81.31% and 31.69% in winter. For a 20 years’ project, using the grid as baseline for the comparison, the lifecycle cost analysis have projected the residential prosumer to break-even after 16.35 years and save 19.5%; while the commercial prosumer can break-even after 5.3 years and save 55.2%. Moreover, this study shows the ability of the developed model to simulate systems with different components, demands, resources as well as costs. The model developed in this study may assist researchers and engineers interested in the optimal operation of prosumers in Peer-to-Peer energy sharing schemes.

Hypothesis of thermal and mechanical energy storage with unconventional methods

There is not a real “storage market” and the range of technical solutions for electrical storage appears to be underdeveloped. The use of electrochemical batteries seems to be the easiest and cheapest way, but some problems related to disposal, average life span and storage capacity, still put a brake on their diffusion. The micro CAES-TES (Compressed Air Energy Storage – Thermal Energy Storage) systems with small renewable energy plants for cogeneration and trigeneration represent an important development perspective thank to the reuse of the heat generated at the stage of air compression (for heating) and air expansion (for cooling). This improves the complexity of the entire system because of the heat exchange and thermal storage units must match the capacities and performances of the air compression/expansion units. The paper presents a new mathematical model for micro CAES-TES systems, implemented in Matlab software environment. The novelty is the use of air compressed energy storage in small and residential applications, a trigeneration due to reuse of heat from air compression and expansion stage, only renewable energy used. By keeping the initial investment low, the analysis is extended to the optimal system configuration and identifies key parameters that have a dominant influence on improving system efficiency and provides useful guidance for CAES-TES system design. The results show that, for an air storage volume of 4 m3, the optimal configuration is with a compression ratio of 15 splitted in two stages, charging time 5 h, mechanical storage efficiency 48%, compression air flow rate 3.73 kg/hour. The proposed system has a possible future development overall if combined with new possible scenarios of direct use of compressed air in the residential sector.

Green hope or red herring? Examining consumer perceptions of peer-to-peer energy trading in the United Kingdom

Across the globe, electricity sectors have seen a relatively large increase in the number of installations of small renewable energy systems, leading to an interest in the potential role of the prosumer. These prosumers (producers and consumers of electricity) could help drive electricity sector transformation, but at present electricity trading is associated with a lack of control and power held by consumers. Peer-to-peer trading schemes between energy consumers are increasingly being reported in the trade press as a new way to empower consumers, especially since the advent of blockchain, an emergent technology that could facilitate the adoption of such schemes. Research to understand how and why electricity trading occurs has received little attention within literature thus far. In this study we investigated the existing elements of electricity trading. A total of 16 structured interviews with domestic consumers, business consumers, domestic prosumers and business prosumers were undertaken. All interviews identified ease of payment as a key theme for electricity trading (although we note that ease may be in tension with sustainability and greater awareness of energy-related environmental impacts). Consumer interviews also identified lack of engagement with the process of receiving energy, and cost, as key themes. Prosumer interviews identified positive associations with power, and personal and business image, as key themes. Therefore, it is recommended that these factors be incorporated into the user interface of blockchain systems, to potentially increase adoption for peer-to-peer trading.

Impacts of Array Orientation and Tilt Angles for Photovoltaic Self-Sufficiency and Self-Consumption Indices in Olive Mills in Spain

Olive mills are extensive in the Mediterranean Basin, and Spain constitutes approximately 45% of global production. The industrial sector faces a new energetic paradigm where distributed generation provided by small renewable energy sources may reduce the dependence from fossil energy sources as well as avoid energy distribution losses. Photovoltaic self-consumption systems can play an important role in confronting this challenge due to their modularity and their decreasing cost. Most of self-sufficiency energy studies are focused on building sector and discussions about the idiosyncrasy of industrial load profiles, and their matching capability with photovoltaic generation profiles can be scarcely found. This work analyzes the potential of photovoltaic self-consumption systems as a function of the array power, array tilt, and orientation angles to face the electric consumption in olive mills. Different recording intervals and reporting periods are considered. Results show that a self-sufficiency index of 40% may be achieved on olive harvest basis. Moreover, due to the load profile particularities, percentage error lower than 1.6% has been found when considering a recording interval of 60 min when matching the olive load consumption and photovoltaic generation profiles. Chosen array tilt and orientation angles may be key parameters to maximize the self-sufficiency index.

A Robot System Maintained with Small Scale Distributed Energy Sources

An energy autonomy system is sustained by energy from independent and distributed sources. This paper presents a robot system that obtains energy from renewable energy sources distributed over a large area with limited storage capacity. We constructed a linearized charge model to estimate the required energy node capacity and distribution for the robot to survive. For a robot to obtain energy from an energy source, it must be able to recognize the energy node and able to receive energy reliably. We used wireless power transfer to solve conventional contact charging problems, such as mechanical complexity and unstable contact, and image information was used to recognize the energy nodes and align the transmission coils accurately. A small scale renewable energy source was constructed and a charge experiment was conducted to verify the proposed autonomy system feasibility.

Environmental Kuznets curve revisit in Central Asia: the roles of urbanization and renewable energy.

Based on the environmental Kuznets curve (EKC) hypothesis, the aim of this paper is to examine the relationships among per capita CO2 emissions, per capita real GDP, per capita renewable energy consumption, and urbanization in a panel of five Central Asian countries (Kazakhstan, Kyrgyz Republic, Tajikistan, Turkmenistan, and Uzbekistan) from 1992 to 2013. For robustness checking, three estimator techniques reveal no evidence of inverted U-shape EKC consistently. Moreover, renewable energy consumption plays negative impact on emissions, while urbanization plays positive, significantly. The findings of heterogeneous panel causality suggest that there are bidirectional causalities; each other expect no causality from emissions to renewable energy. Finally, some implications, such as developing a small renewable energy project and sustainable urbanization and strengthening in-regional and out-regional cooperation, are given in this region.

Renewable Energy Communities in the Law of the EU, Australia, and New Zealand

The article juxtaposes the regulatory approach to small renewable energy sources and energy communities in the European Union, Australia, and New Zealand, highlighting such matters as the nature, character, and scope of the regulatory model of renewable energy sector. The paper also analyses energy communities in the past, current and drafted European law (as in the "Clean Energy for all Europeans" package) as well as discussing relevant legislation and policies on small renewable energy sources and energy communities in Australia and New Zealand. In this context, this article reviews the possibility of exporting the European model on energy communities outside the EU.

A Unified Model for the Optimal Management of Electrical and Thermal Equipment of a Prosumer in a DR Environment

Due to the recent trend toward the decentralization of energy production, i.e., the presence of small renewable energy plants directly connected to the grid, end users are fostered to pro-actively participate to the energy management by joining the so-called demand response programs. In addition, groups of end users are encouraged to form energy districts in which the energy is exchanged locally and negotiated, without intermediaries, directly with the energy providers. In this paper, a demand response program is envisioned at the energy district level, where an aggregator dynamically determines the energy prices on the basis of market conditions, and a Cloud component is in charge of supplying high-level aggregated information. End user dwellings are purposely equipped in order to retrieve information from the Cloud so as to establish the best energy management strategy. This strategy is determined by solving an optimization problem called “prosumer problem.” The model underlying the prosumer problem takes into account both thermal and electrical components at the same time. Experimental results show the benefits of this unified thermal and electrical model in terms of improved energy efficiency and reduction of energy costs.