Energy communities (ECs) are essential tools to meet the Energy Transition goals but, to fully unleash their potential, they require a coordinated operation and design that the community itself may ...be ill-equipped to manage. Aggregators and Energy Service COmpanies (ESCOs) can perform this support role, but only provided that their goals are aligned to those of the community, not to incur in the agency problem. In this study, we propose a business model for aggregators of ECs, and its optimization problem, accounting for all crucial aspects: (i) alleviating the risk of the agency problem, (ii) fairly distributing the reward awarded to the EC, (iii) estimating the fair payment for the aggregator services, and (iv) defining appropriate exit clauses ruling what happens when a user leaves the EC. A mathematical model is developed, employing several fair game-theoretic reward distribution schemes, some of which are proposed here for the first time. A case study is developed, and results show that the aggregator enables reducing costs by 16% and improving renewable penetration and self/shared consumption by 35%–51% with respect to the base case. Our results suggest that the aggregator fair retribution is around 16%–24% the added benefit produced with respect to the base case, and that stable reward distribution schemes, such as Shapley/Core, Variance/Core or Nucleolus, are stable and recommended. Moreover, the results highlight the unwanted effect that some non-cooperative ECs may have an added benefit without providing any positive effect to the power system. Our work provides a methodology and preliminary results that can help policy makers and developers in tailoring national-level policies and market-offerings.
•Cooperative and non-cooperative optimal sizing of Energy Communities: a comparison.•Business model with fair stable profit allocation and withdrawal/termination clauses.•Comparison of Shapley Value, Core, Nucleolus, MinVariance and novel hybrid methods.•Role, value and fair remuneration of aggregators based on literature review.•Effects on the total peak power that affects the distribution network.
Increasing the self-consumption of photovoltaic (PV) power is an important aspect to integrate more PV power in the power system. The profit for the PV system owner can increase and the stress on the ...power grid can be reduced. Previous research in the field has focused on either self-consumption of PV power in individual buildings or PV power curtailment for voltage control. In this paper self-consumption of residential PV power in a community of several single-family houses was investigated using high-resolution irradiance and power consumption data. Cases with individual or shared battery energy storages for the houses were examined. PV power curtailment was investigated as a method to reduce feed-in power to the grid, i.e. peak shaving. Results indicated that the self-consumption ratio increased when using shared instead of individual storage. Reducing the feed-in power from the community by almost 50% only led to maximum 7% yearly production losses due to curtailment and storage losses. The economics for shared storage are slightly better than for individual ones. These results suggest that residential PV-battery systems should use (i) shared energy storage options if local regulations allow it and (ii) PV power curtailment if there are incentives to lower the feed-in power.
•High increment in PV self-consumption in a community using shared grid connection.•Higher self-consumption with centralized than individual battery storage in houses.•Halving of peak power to grid by PV power curtailment with annual losses below 7%.•Higher annual revenue from shared than individual battery storage.
On the Capacity of MIMO Optical Wireless Channels Li, Longguang; Moser, Stefan M; Wang, Ligong ...
IEEE transactions on information theory,
2020-Sept., 2020-9-00, 2020-09, Letnik:
66, Številka:
9
Journal Article
Recenzirano
Odprti dostop
This paper studies the capacity of a general multiple-input multiple-output (MIMO) free-space optical intensity channel under a per-input-antenna peak-power constraint and a total average-power ...constraint over all input antennas. The focus is on the scenario with more transmit than receive antennas. In this scenario, different input vectors can yield identical distributions at the output, when they result in the same image vector under multiplication by the channel matrix. We first determine the most energy-efficient input vectors that attain each of these image vectors. Based on this, we derive an equivalent capacity expression in terms of the image vector, and establish new lower and upper bounds on the capacity of this channel. The bounds match when the signal-to-noise ratio (SNR) tends to infinity, establishing the high-SNR asymptotic capacity. We also characterize the low-SNR slope of the capacity of this channel.
Markets are changing as the result of (1) the addition of variable wind and solar that causes highly volatile electricity prices and (2) the goal of a low-carbon economy. These changes require ...economic low-carbon dispatchable electricity, which is now provided by natural gas turbines, and dispatchable heat for industry and commerce. Moreover, nuclear plant requirements have changed in the last 50 years with high capital costs in western countries. An alternative plant design is described with the nuclear island separated from a nonnuclear power block by large-scale heat storage. All heat from the reactor is sent to heat storage. The nuclear reactor operates at base load and is sized to meet average energy demand over a period of days. Heat storage provides variable heat to industry and/or the power block. The nonnuclear power block is sized to provide peak electricity capacity (kilowatts) several times the nuclear reactor base-load power output to maximize revenue by sale of electricity at times of high prices. The power block capital cost (heat exchanger, turbine, and generator) per unit of generating capacity (kilowatt) is less than a conventional gas turbine that includes heat generation (compressor and burner) and the power block (turbine and generator). Nuclear reactor capital cost is reduced by fewer requirements on the nuclear system (not connected to the grid) and nuclear-quality construction for only the reactor. Operating costs (security, maintenance, etc.) are minimized by separation of the nuclear reactor plant from balance of plant. Low-cost heat storage provides a competitive economic advantage to heat-generating technologies (nuclear, concentrated solar power) over electricity-generating technologies (wind, solar, photovoltaic) with more-expensive battery or other electricity storage systems in providing dispatchable electricity to the grid.
The development of nonprecious metal‐based electrocatalysts for the oxygen reduction reaction holds the decisive key to many energy conversion devices. Among several potential candidates, transition ...metal and nitrogen co‐doped carbonaceous materials are the most promising, yet their activity and stability are still insufficient to meet the needs of practical applications. In this study, a core–shell hybrid electrocatalyst is developed via the self‐polymerization of dopamine and cobalt on carbon nanotubes (CNTs), followed by high‐temperature pyrolysis. The polymer‐derived carbonaceous shell contains abundant structural defects and facilitates the formation of CoN/C active sites, whereas the graphitic carbon nanotube core provides high electrical conductivity and corrosion resistance. These two components separately fulfill different functionalities, and jointly afford the catalyst with excellent electrochemical performance. In 1 m KOH, CoN/CNT exhibits a positive half‐wave potential of ≈0.91 V, low peroxide yield of <7%, as well as great stability. When used as the air catalyst of primary Zn–air and Al–air batteries, this hybrid electrocatalyst enables large discharge current density, high peak power density, and prolonged operation stability.
CoN/carbon nanotube core–shell hybrid electrocatalyst is developed via the self‐polymerization of dopamine and cobalt on carbon nanotubes followed by high‐temperature pyrolysis. It exhibits an excellent electrocatalytic activity for the oxygen reduction reaction, and can serve as the air catalyst to enable high‐performance primary Zn–air and Al–air batteries.
•Combining thermal storage with an air source heat pump to provide space cooling.•Thermal storage can reduce electrical energy and power needed for space cooling.•Techno-economic analysis of thermal ...storage for space cooling is necessary.•The uptake of energy storage for space cooling requires economic incentives.
Space cooling is the main contributor to high electrical power demand in summer. This research investigates the effect of adding a phase change thermal energy storage unit (PCTSU) to an air source heat pump (HP) cooling system. The HP model improves on an existing model in the simulation software library to simulate the HP performance. The PCTSU performance is simulated using a newly developed two-dimensional transient heat transfer model, which is experimentally validated against available experimental results. The cooling system is operated in three modes to satisfy the space cooling demand of a 7.6 stars house in the City of Adelaide, Australia. The PCTSU is charged by the HP when outdoor temperature is relatively low and discharged either whenever space cooling is required during the day (mode M2) or during the peak period only (mode M3). The simulation is conducted for the whole cooling season, and the cooling energy and electricity usage performances of the system with a PCTSU (modes M2 and M3) are compared with those of the system without a PCTSU (mode M1). A sensitivity analysis reveals that the PCTSU performance is slightly sensitive to the uncertainties of melting temperature of the phase change material and to the inlet temperature of the heat transfer fluid. The PCTSU provides 25% and 13% of the cooling energy and requires 11% and 6% of the electrical energy usage for charging by the HP in modes M2 and M3 respectively. Both electricity usage and demand tariffs are considered, and the cost savings are 14% and 7% in the former and 14% and 13% in the latter, in modes M2 and M3 respectively. The cost analysis indicates that techno-economic benefits of using PCTSUs should be carefully analysed. Appropriate economic incentives are needed to accelerate the uptake of thermal storage for space cooling applications to reduce high electrical power demand and help to avoid the need to further increase the grid capacity.
Around the globe, renewable energy sources and their associated technologies are critical to power generation. The solar photovoltaic (PV) system is one of the renewable energy systems supporting ...electricity consumption in the residential domain. Despite the potential of solar PV as well as an appreciable amount of global solar radiation in the region, no previous study has examined the viability of the PV system for off-grid electricity production in Jos, Nigeria. This paper focuses on examining the feasibility of deploying an off-grid PV system to drive the electricity consumption of a residential building in Jos, Nigeria (9.9ON, 8.9OE, 1204.87 m). The paper adopts a mathematical modelling method for designing and analyzing the entire PV systems to drive the power consumption of the households. By applying mathematical modelling approach, the results demonstrate that 10 MLE275HD2 PV modules each of 275 Wp and five batteries of 100 Ah can satisfy the annual electricity consumption of approximately 3132 kWh. Further, an economic analysis carried out by using the life-cycle cost (LCC) analysis depicts that the LCC, the annualized life-cycle cost (ALCC) and cost of electricity (COE) to be US$ 10,110.85, US$ 593.75 and US$ 0.18/kWh respectively. The results of this modelling demonstrate both the technical and economic viability of the off-grid PV system for power generation, and can serve as a model to the successful development of the system for real application. Further, the model can encourage the stakeholders in the renewable sector to provide the support mechanisms towards the adoption of the PV system in the residential buildings.
•Mathematically modelling application to determine the techno-economic parameters of an off-grid solar PV in Jos, Nigeria.•Proven methodology to estimate for sizing the standalone PV systems to drive electricity in the residential buildings.•The cost of electricity is proven to be feasible and applicable to support residential buildings’ electricity consumption.
To evaluate the continuous and instantaneous load capability of a battery, this paper describes a joint estimator for state-of-charge (SOC) and state-of-function (SOF) of lithium-ion batteries (LIB) ...based on Kalman filter (KF). The SOC is a widely used index for remain useful capacity left in a battery. The SOF represents the peak power capability of the battery. It can be determined by real-time SOC estimation and terminal voltage prediction, which can be derived from impedance parameters. However, the open-circuit-voltage (OCV) of LiFePO4 is highly nonlinear with SOC, which leads to the difficulties in SOC estimation. To solve these problems, this paper proposed an onboard SOC estimation method. Firstly, a simplified linearized equivalent-circuit-model is developed to simulate the dynamic characteristics of a battery, where the OCV is regarded as a linearized function of SOC. Then, the system states are estimated based on the KF. Besides, the factors that influence peak power capability are analyzed according to statistical data. Finally, the performance of the proposed methodology is demonstrated by experiments conducted on a LiFePO4 LIBs under different operating currents and temperatures. Experimental results indicate that the proposed approach is suitable for battery onboard SOC and SOF estimation.
•A linearized battery model is developed for on-board implementation.•A KF-based co-estimator for battery SOC and SOF is proposed.•The robustness of joint estimator is evaluated under various scenarios.•The statistical analysis for influential mechanism of SOF factors are performed.
Anion exchange membrane fuel cells (AEMFCs) have advanced rapidly in the past four years, while the majority of the state-of-the-art AEMFCs relies on unrealistic and uneconomical operating ...conditions, particularly a high hydrogen flow rate (>1000 mL min−1). Here, we report a poly(fluorenyl aryl piperidinium) (PFAP) ionomer that enables high power of AEMFC with low hydrogen flow rate (≤100 mL min−1 for 5 cm2 cell). The high water permeability of the ionomer is beneficial to prevent anode flooding under moderate relative humidity. The relationship between hydrogen flow rate and limiting current density is revealed based on PFAP copolymers. Specifically, the peak power density of AEMFC is 1.77 W cm−2 with a H2 flow rate of 75 mL min−1, retaining >70% power density from the H2 flow rate of 1000 mL min−1 (2.42 W cm−2). Importantly, the present AEMFCs display much higher hydrogen utilization efficiency above 90% and hydrogen fuel power (∼30 W cm−2 L−1) than previously reported AEMFCs (<30% and 0.4–3.5 W cm−2 L−1). Moreover, the present AEMFCs show stable cell performance with a low hydrogen flow rate at 70 °C for >110 h.
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•Limiting current density and H2 utilization efficiency are elucidated in AEMFCs.•AEMFCs using realistic and low H2 flow rate reach the power density >1.9 W cm−2.•Present AEMFCs display outstanding hydrogen fuel power of 10–34 W cm−2 L−1.
Here we revealed that lasers with lower repetition rates (5 kHz and 50 kHz) from an amplifier were more efficient in SHG imaging than a laser with high repetition rate (80 MHz) from an oscillator, ...demonstrating that peak power played a more important role than the repetition rate for high SHG yield. Although lasers with relatively high peak power damaged the cancer cells used in the imaging at a relatively lower laser power, better signal/noise ratio was achieved before the occurrence of the adverse damage. It was also revealed that photobleaching was avoided with the lower repetition rate lasers. Furthermore, the three lasers were applied in analyzing the scattered SHG intensity from colloidal BaTiO3 nanoparticles using photon counting method. All tests with the three lasers reached satisfactory results. Importantly, the lasers with low repetition rates showed great potential in the detection of weak nonlinear scattering.
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