Discounted Payback Time Research Articles

An economic analysis of tidal energy to support sustainable development

Decarbonization of the energy sector, requires a strong expansion of renewable energy, which combined with effective and efficient use of resources, enables the development of models based on the green economy. Tidal energy, which is currently underutilized, can contribute to this change by providing affordable and clean energy, thus contributing to sustainable development. This work evaluates the economic dimension of sustainability and provides a profitability analysis related to a 1 MW plant located in central Italy. The methodology consists of a technical framework, geared toward quantifying the energy potential from that plant, and economic models based on indicators such as Net Present Value (NPV), Levelized Cost of Energy (LCOE) and Discounted Payback Time (DPBT).The results show that the plant turns out to be profitable in the base case (NPV = 573 k€ and DPBT = 21 years) and policy interventions, which see the use of capital grants and subsidies, change the results to NPV ranging between 338 and 1287 k€ and DPBT between 11 and 15 years. However, alternative scenarios indicate that the variables that most impact economic outcomes are changes related to energy selling price and capacity factor. The LCOE in the different scenarios varies between 49.4–89.8 €/MWh. The implications of this work define that tidal energy supports the energy transition to sustainable development and that the mix of technical, market, and political factors must be considered in policy decision making.

Net metering rolling credits vs. net billing buyback: An economic analysis of a policy option proposal for photovoltaic prosumers

There is a need for a methodology that allows the prosumer to implement a policy of choosing different compensation mechanisms. Thus, we propose the economic equivalence between net metering rolling credit (NM-RC) and net billing buyback (NB-BB) by defining a breakeven price (BP) for NB-BB that equals the Net Present Value (NPV) of these two options and using Discounted Payback Time (DPBT) as a tiebreaker metric. The Brazilian scenario was used for validation. When using the retail price, the NPV values for the NM-RC mechanism were lower in all scenarios (mean NPV of US$ 3958.66 in NM-RC against US$ 4372.17 in NB-BB). It is possible to observe that the BP that equalizes the two mechanisms is generally lower than the tariff charged by the utility (mean BP is US$ 0.1111 while mean tariff is US$ 0.1838), which reveals that offering this choice option does not burden the system. The NM-RC was selected in four cities, and the NB-BB was chosen in three cities. This policy could encourage potential prosumers, who often feel reluctant to invest in PV-DG owing to the long payback period. Thus, the political schemes complementing the compensation mechanism are relevant, especially for continental-sized countries with many utilities.

Synergizing hybrid renewable energy systems and sustainable agriculture for rural development in Nigeria

This research explores the viability and importance of implementing Hybrid Renewable Energy Systems (HRES) in Nigeria's agriculture sector. Despite progress, most rural regions still struggle with unreliable electricity. HRES provides a way to power agricultural endeavors while promoting sustainability, economic viability, and ecological conservation. A case study involving renewable energy applications for powering a typical Nigerian farm facility is also presented. Based on the review's findings, while 53.1 % of the journals analyzed were primarily concerned with community load, the agricultural sector received much less coverage, especially in rural areas. For the case study, solar PV dominates the HRES (98.3 %) electricity production, with biogas and wind turbines contributing the rest. The project costs $1,782,602 over 25 years, with competitive energy costs and a discounted payback time of 7.22 years. Environmentally, carbon dioxide emissions are negligible (16 kg/yr), and excess electricity production offers income potential for the farm facility. Overall, HRES is presented as an environmentally beneficial and cost-effective way to change rural farm operations, emphasizing the critical need to integrate energy and agriculture. Still, challenges such as inaccurate data, inadequate infrastructure, and inconsistent policy dynamics remain. In addition, the work highlights an area where more study is needed, namely the use of MCDM analysis for selecting the optimal energy system based on multiple criteria. Utilizing HRES in agriculture is consistent with the SDGs and will increase agricultural productivity, self-sufficiency, and environmental friendliness in Nigeria.

New models for feasibility assessment and electrolyser optimal sizing of hydrogen production from dedicated wind farms and solar photovoltaic farms, and case studies for Scotland and Vietnam

Although green hydrogen produced from dedicated wind and PV plants is considered an alternative route to achieve net zero targets, its assessment models are only being developed in recent years. Even though electrolyser is known to account for a large portion of the investment costs, there is still a lack of sizing models for this equipment, which can negatively affect the feasibility of plants. Moreover, the impacts of future technology maturity and cost reduction on the feasibility of hydrogen production plants are rarely analysed and reported. Realising the research gaps from previous studies, this paper proposes a comprehensive feasibility assessment model for green hydrogen production from dedicated offshore wind and PV plants, utilising net present value, discounted payback time, and levelised cost of energy and of hydrogen (LCOH) as economic evaluation criteria. Furthermore, a unique sizing model is presented, allowing the optimal electrolyser size with the lowest LCOH to be found. Two case studies investigating a hypothetical offshore wind farm in Scotland and a hypothetical PV farm in Vietnam to produce green hydrogen have been carried out, in which the impacts of technology maturity and cost reduction on the LCOH are analysed. It is projected that the LCOH in Scotland and Vietnam case studies, with specific conditions and assumptions of the two cases, would reduce from 3.10 and 3.05 $/kg in 2030 to the lowest values of 2.16 and 1.59 $/kg in 2050, respectively. Additionally, the optimal electrolyser capacity is found to equal 89.3% of the offshore wind plant capacity, and 57.7% of the PV plant capacity. Finally, a sensitivity analysis is conducted, which revealed the capital cost of renewable energy plants has the most significant effect on the final LCOH.

4th generation district heating (4GDH) in developing countries: Low-temperature networks, prosumers and demand-side measures

The aim is locating low-cost renovation measures to support the efficiency of district heating (DH). The topology analysis and GIS Zulu© are applied for hydraulic simulation and to verify the scenario viability. The scenarios are compared by life cycle cost, levelized cost of heat (LCoH), capital and operational costs, energy production and consumption, network length, heat losses, linear heat density, heat pump usage, peak load reduction, nominal power duration or the equivalent full load time. As demand-side measures (DSM), improved control, thermostats with an indoor temperature sensor and variable frequency drive (VFD) pumps reduce heat demand. Prosumer scenario imply installing a base-load heat pump. It means a consumer no longer receives heat from the DH system, because the households are now adapted to lower space heating (SH) supply temperature. Prosumer concept also allows placing a heat pump on the DH return line. The simplest configuration includes only the booster heat pump and domestic hot water (DHW) tank storages enough to cover morning or evening consumption peak. To limit piping cost, only supply and return pipes are considered for low-temperature DH, no additional (service) pipes or mixing valves are assumed. Converting single-family houses to prosumers decreases energy consumption, primary network flows and temperatures. LCoH ranges 19.7-35.4 EUR/MWh, depends on the decommissioned pipe length and its proportional pipe investment cost. LCoH decreases as the share of consumers converted to prosumers increases. Discounted payback time is 10 years for DSM and 41 years for prosumer case. For a base-load heat pump, the payback time is much higher than the reference scenario. It implies the same share of heat losses (16% of heat supplied from the CHP plant) with generally worse environmental and energy saving effect due to higher greenhouse gas (GHG) emissions and higher consumption of primary energy. Energy production is expected to follow the pattern of the useful energy consumption to compensate heat losses. The effects are decreasing residential heat demand (-4%), additional capacity to connect new consumers (+6%) and decreasing the network length.

Techno-economic evaluation of photovoltaic thermal system integrated with porous phase change materials: Case studies in China

This study aims to to develope a comprehensive mathematical model for predicting the performance, environmental impact, and economic viability of solar photovoltaic thermal (PVT) systems, with specific focus on the use of Porous Phase Change Material (PPCM) into a PVT system (PVT-PPCM) and its effect on the cooling cycle temperature throughout the year. The model was experimentally validated and implemented in Matlab to assess the performance of various systems, including PV-only, PVT, and PV integrated with PCM (PV-PCM). To determine the optimum melting point temperature for the PCM-based systems, a sensitivity analysis was conducted for different locations in China. The annual performance, CO2 reduction, discounted payback time (DPBT), and Levelized cost of energy (LCOE) were predicted for each system. Subsidy-free method was used for economic evaluation, which only shows system’s cost savings. In addition, it is worth noting that the maximum power output of each system was evaluated to be 1 MW. The results of the study showed that PVT-PPCM exhibited the highest annual power output of 1920 MWh and CO2 reduction of 30 tons/year, while the LCOE ranged from 0.02 to 0.58 CNY/kWh and the DPBT varied from 5 to 20 years across the case studies. The study also compared the Levelized cost of electricity (LCOEel) of PVT and PVT-PPCM with cases in UK and Spain, with the lowest LCOEel of PVT recorded in Kunming at 0.4 CNY/kWh.The significance of this study lies in its identification of the strengths and weaknesses of PVT system designs across different climates, highlighting areas for improvement. By providing insights into system performance, environmental impact, and economic feasibility, this research contributes to the advancement and optimization of PVT technology for sustainable energy applications.

Recovery of Metals from Printed Circuit Boards by Gold-REC 1 Hydrometallurgical Process

The paper describes a small full-scale plant based on the Gold-REC 1 process, designed and patented by the University of L’Aquila; the hydrometallurgical process allows the treatment of printed circuit boards (PCBs). The first step is a mechanical treatment to reduce the size of the scraps below 2 mm. The extraction of base metals occurs in a first reactor by a sulfuric acid/hydrogen peroxide solution. After filtration, the solid is leached again with thiourea and ferric sulfate in a sulfuric acid solution to extract gold and silver. This second solution is sent to an electrolytic cell where gold is recovered as metal powder. The resulting solution undergoes a second electrowinning, where silver is deposited on the cathode. The first pregnant solution undergoes recovery of Cu and Sn. A simulation was developed using lab-scale trial results. The 350 tons PCBs/year, running in a batch operating mode, produces around 43.8 kg/year of gold, 85.8 kg/year of silver, 42.4 tons/year of copper, and 7.2 tons/year of tin oxide. The results show the profitability of the process: the net present value is EUR 10.7 M, with an internal rate of return of 150% and a discounted payback time of 2 years.

Charging private electric vehicles solely by photovoltaics: A battery-free direct-current microgrid with distributed charging strategy

Charging electric vehicles (EV) by photovoltaics (PV) contributes to achieving carbon neutrality, but puts pressure on urban renewal, e.g., large investments in distribution grid upgrade and energy storage (ES). To solve this problem, we proposed a charging system aiming at providing intermittent but free solar charging service for private EV drivers to cover their daily intra-urban transportation demand. It is a battery-free direct-current (DC) microgrid with a distributed charging strategy, taking variable DC bus voltage as a control signal. The system was optimized and tested by simulation on an office building with 80 private EVs. We performed a system performance comparison, when achieving the same guarantee level of EV use with the parking shed fully cover by PV. A 10-kW charger (DC Level 1) with the strategy can take the role of a 3.5-kW charger (AC Level 2) with ES (26.0 kWh/parking space) to coordinate PV generation and charging load. Furthermore, connecting the system with the adjacent building can increase the annual solar self-consumption rate from 33.3% to 67.9%, and avoid the distribution grid upgrade (average 5.6 kVA/charger). The discounted payback time of this building-connected system decreases from 9.4 to 4.5 years, compared with a conventional solar charging station.

Computational tool for technical-economic analysis of photovoltaic microgeneration in Brazil

This paper proposes a new computational tool, called SolarEnergy, which was implemented through an innovative methodology to perform technical-economic analysis of photovoltaic (PV) microgeneration in Brazil. SolarEnergy calculates energy flow and energy bill savings based on the rules of the Brazilian NEM scheme. From the maximization of the net present value, SolarEnergy provides the optimal nominal power according to the orientation and slope of PV panels and the electricity consumption profile. This functionality is crucial to avoid undersizing or oversizing, which commonly occurs in practice. In addition, the tool provides the following information: (i) electricity generation, (ii) net present value, (iii) modified internal rate of return, (iv) discounted payback time, and (v) sensitivity analysis of key parameters (e.g., nominal power, pv system cost, electricity tariff, and minimum attractive rate of return). Currently, such particularities are characterized as relevant differences in relation to other computational tools. The validation and applicability of SolarEnergy are demonstrated from case studies of PV systems installed in the state of Goiás, Brazil.

Experimental and techno-economic analysis of two innovative solar thermal receiver designs for a point focus solar Fresnel collector

In this paper, techno-economic analysis and the experimental campaign for a new solar concentrating system are presented. Two novel receivers (Jet impingement receiver with mesh structure & helical channel receiver) are tested on a novel collector technology. The collector technology integrates the two established models of solar concentrating technologies, which are linear Fresnel reflector technology and central receiver technology, into the new concept called the Point Focus Fresnel Collector (PFFC). It is found that the PFFC system with jet impingement receiver and mesh structure provides higher thermal efficiency and manufacturing ease compared to parabolic dish systems. Maximum thermal efficiency of jet impingement receiver is highest at 87% whereas that for helical channel receiver is 83%. Average thermal efficiency of jet impingement receiver is 61% whereas that for helical channel receiver is 58%. Economic analysis of the system reveals that the discounted payback time for the PFFC system is only 5.5 years and less than one year compared to diesel and electricity powered steam generators respectively at an inflation rate of 2.5%. Substantial saving is predicted with PFFC system compared to diesel and electricity powered steam generator. For all discount rates in the range of 2.5–25%, the levelized cost of energy (LCOE) for PFFC system is much lower than that of LCOE in Saudi Arabia for conventional system. Since the LCOE in most of the Middle East and North Africa (MENA) countries is higher than the LCOE in Saudi Arabia, therefore, the PFFC system is also suitable for other MENA countries where average direct normal irradiation values are comparable to Saudi Arabia.

Net-metering and Feed-in-Tariff policies for the optimum billing scheme for future industrial PV systems in Bangladesh

In this paper, the economic sustainability of net billing and feed-in-tariff (all energy buy/sell) method is analyzed in comparison with the current net-metering for the industrial PV systems in Bangladesh. Three billing methods are compared according to plant capacity factor, excess energy transfer, levelized cost of energy (LCOE), net present value (NPV), payback period, and profitability index (PI) for the analysis of optimum billing scheme. The highest plant capacity factor and minimum LCOE are found for the large PV system in Chattogram. Out of three methods, all energy buy/sell exhibits the NPV which is USD 5.85 million and PI of 2.54 at the minimum 4.9 years discounted payback time for the large PV system in Chattogram. The sensitivity analysis of solar irradiation at six other regional areas, bill escalation rate, and discount factor is performed to observe the impact on annual energy production and NPV. For both systems, all three assessed methods are found economically feasible, but the net metering is attained as the least profitable in comparison with net billing and all energy buy/sell schemes. From various analyses, it is found that the adaption of these two schemes in the present guideline can enhance industrial PV production in Bangladesh.

Techno-economic analysis of a micro-scale biogas plant integrated with microalgae cultivation for the treatment of organic municipal waste

The deployment of small-scale anaerobic digestion (AD) plants for the treatment of the organic fraction of municipal solid waste (OFMSW) and associated production of renewable energy at a local level has recently attracted attention as opposed to full-scale centralized plants. In this work, we evaluate the technical and economic feasibility of an integrated process comprising small-scale AD of OFMSW followed by microalgae cultivation, to valorise the waste streams of the former (off-gases produced by combined heat and power generation and liquid digestate) for the production of valuable biomass to be destined to either the biofertilizers or the biostimulants markets, in agreement with a circular economy perspective. The material and energy balances were obtained by means of process simulation for a plant located in Northern Italy, taken as a reference. The analysis revealed that, although the high turbidity of the digestate strongly hinders biomass production, the process is profitable from a techno-economic perspective, with discounted payback time ranging from 3.3 to 7.1 years, and profitability indexes greater than 1. The low market price of biofertilizers makes it the less profitable choice, even compared to the AD process alone, while selling the biomass for biostimulants applications could strongly increase the process profitability.

Techno-economic analyses of power-to-ammonia-to-power and biomass-to-ammonia-to-power pathways for carbon neutrality scenario

In the energy system transition, energy storage technology is vital for increasing the penetration of renewables, where chemical energy storage is most suitable for long-term grid-scale energy storage. Green ammonia is selected to replace hydrogen for the sake of storage efficiency, safety, and cost. Most time, ammonia is seen as either an energy storage medium or a fuel. However, the dual identity of ammonia as an energy carrier is discussed less. So, this study conceptualizes power-to-ammonia-to-power (P2A2P) and biomass-to-ammonia-to-power (B2A2P) pathways where ammonia is served as an energy carrier for both energy storage and fuel. Eight scenarios involving recent ammonia production and utilization technologies are technically and economically evaluated based on hourly weather and demand data. The results show that the B2A2P pathway presents a better performance because the average energy and exergy efficiencies are hardly influenced by the supply and demand balance of electricity. They can reach 40–50% in contrast to 27–47% in the P2A2P pathway. Besides, the B2A2P pathway provides a considerable amount of ammonia (around 10,000 t/month), which takes the major part of revenues. Although the CAPEX (603.3–675.1 MUSD) and OPEX (30–40 MUSD) in the B2A2P pathway are much higher than that of P2A2P (159.2–181.1 and 6–9 MUSD, respectively), the optimal scenario of the B2A2P pathway has a shorter discounted payback time (six years), and higher net present value (415.5 MUSD).

Design and Costs Analysis of Hydrogen Refuelling Stations Based on Different Hydrogen Sources and Plant Configurations

In this study, the authors present a techno-economic assessment of on-site hydrogen refuelling stations (450 kg/day of H2) based on different hydrogen sources and production technologies. Green ammonia, biogas, and water have been considered as hydrogen sources while cracking, autothermal reforming, and electrolysis have been selected as the hydrogen production technologies. The electric energy requirements of the hydrogen refuelling stations (HRSs) are internally satisfied using the fuel cell technology as power units for ammonia and biogas-based configurations and the PV grid-connected power plant for the water-based one. The hydrogen purification, where necessary, is performed by means of a Palladium-based membrane unit. Finally, the same hydrogen compression, storage, and distribution section are considered for all configurations. The sizing and the energy analysis of the proposed configurations have been carried out by simulation models adequately developed. Moreover, the economic feasibility has been performed by applying the life cycle cost analysis. The ammonia-based configurations are the best solutions in terms of hydrogen production energy efficiency (>71%, LHV) as well as from the economic point of view, showing a levelized cost of hydrogen (LCOH) in the range of 6.28 EUR/kg to 6.89 EUR/kg, a profitability index greater than 3.5, and a Discounted Pay Back Time less than five years.

Optimal sizing of residential battery systems with multi-year dynamics and a novel rainflow-based model of storage degradation: An extensive Italian case study

Residential battery storage to perform load shifting and demand side management has become of utmost importance to improve hosting capacity, increase renewable energy penetration and meet environmental targets, especially with energy community policies. As the lifetime of electrochemical batteries depends upon their scheduling and environmental conditions, the multi-year effects of operational strategies can affect the economics of the investment. However, rarely complete long-term simulations of the operation of storage systems are performed to assess the battery profitability including the operational effects of aging, and limited studies account for a large statistics of consumers. In this study, we propose a multi-year sizing methodology for residential applications, where the complete lifetime of batteries is simulated at 15-min time resolution till complete degradation using an improved non-linear non-convex degradation model; the photovoltaic plant aging is also considered. An extensive analysis on the economics and commercial size best suited for 399 real load profiles in Italy is proposed. Results suggest that the break-even price of the storage is about 400 €/kWh, which is lower than the average commercial price, and that, as reviewed, current market components may be unfit for consumers with low energy demand. Net Present Value (NPV) and Discounted PayBack Time (DPBT) can reach 500-1500 € and 8-11 years.

Economic Feasibility of Photovoltaic Micro-Installations Connected to the Brazilian Distribution Grid in Light of Proposed Changes to Regulations

Brazil is currently undergoing changes to regulations on distributed generation (DG), specifically for solar energy micro-generation. The changes proposed by the Brazilian Regulatory Agency suggest that only the cost of energy be compensated to investors. The service costs and other charges related to energy tariffs must be divided among consumers. Investors with existing installations and class entities have contested these proposals, calling them “sun-fees”. To date, no scientific papers have been published discussing these changes. The new regulations propose an end to cross subsidies, where all consumers (even those who do not have DG) pay for the transmission and distribution systems. This study compares the economic feasibility of micro-generation before and after implementing the new standards proposed by the regulatory agency. We used data on average electrical energy demand, energy price, and solar radiation in different regions. The national averages were used as a base comparison with other scenarios. The results show that projects are viable for all analyzed scenarios, however, after implementing the proposed changes, the discounted payback time is extended. This, however, does not make projects unfeasible.

Techno-economic study of photovoltaic systems performance in Shiraz, Iran

Regarding the global increasing trend of photovoltaic (PV) installations, it is necessary to examine their performance under different climatic conditions. In this study, a three years of experimentation was carried out in order to evaluate soiling loss, yearly degradation and economic viability of PV systems in the south-central Iran. The results showed that dust effect in consecutive years can be significantly different. For instance, soiling loss in summer of 2017 and 2019 was 6.9% and 7.7%, respectively, whereas this value was 26.4% in summer 2018 due to a sand storm. The yearly average degradation of PV module was evaluated 1.17%, which was significantly lower than the degradation rate found by considering only first two years operation of PV module. In the economic analysis part of the research, a typical 1 MW solar plant was modeled in PVsyst software by using the measured data. The economic assessment showed that investment in PV industry without any special government support is economically profitable, as net present value (NPV) and discounted payback time (DPT) were found 1,367,499 US$ and 5.82 years, respectively. Also, levelized cost of electricity (LCOE) was 0.099 US$/kWh, which could be reduced to 0.054 US$/kWh by providing loan for investment costs.

An energy paradigm transition framework from negative towards positive district energy sharing networks—Battery cycling aging, advanced battery management strategies, flexible vehicles-to-buildings interactions, uncertainty and sensitivity analysis

In response to the clean power production with large-scale deployment of renewable systems, technical challenges are proposed, including the resilient and smart building system design, cycling aging of battery storages, energy congestion between renewable and flexible grid energy, the flexible micro-grids to energy supply fluctuations in multi-energy systems, and so on. In this study, a series of technical solutions, including the integration of plug-in vehicles (under multi-directional energy interaction paradigms), the Vehicles-to-Buildings interaction levels, and the grid-responsive control, were proposed, studied, and discussed to promote the resilient and smart energy systems from district levels in subtropical regions. Dynamic battery cycling aging and advanced modelling tool in this study outperforms traditional rough battery cycling aging approaches, and correct conclusions on battery and vehicle-to-building interaction, to avoid the battery performance overestimation. Novel energy management strategies advance traditional power flow strategy, in terms of the off-peak grid electricity shifting, the enhancement of renewable penetration, and the deceleration of battery cycling aging. Techno-economic performances have been investigated, including net present value (NPV), the discounted payback time (DPT), and the net direct energy consumption (DEC). Furthermore, the energy paradigm transition from negative to positive building–vehicle systems outperforms single case study in academia for carbon-neural transition. The research results showed that, with the energy paradigm transition from the negative to the positive system, the net present value increases from −7.182 × 107 to 5.164 × 108 HK$, and the average annual net DEC decreased from 249.1 to −343.3 kWh/m2.a. Furthermore, compared to Control Strategy 2 (grid-responsive control strategy), the proposed Control Strategy 3 (battery-protective control strategy) can improve the net present value, and the increasing magnitude is dependent on the specific energy paradigm. Furthermore, compared to the positive buildings-vehicle system, the impact of the vehicle-to-building interaction on the decreasing magnitude of the net present value is more prominent for the negative system. The uncertainty and sensitivity analyses indicate that the net present value of the positive energy paradigm as compared to the negative energy paradigm is more sensitive to the battery cost. This study demonstrates the techno-economic performance of district building–vehicle systems with the energy paradigm transition from the negative to the positive, together with a series of effective solutions. The research results can provide multi-dimensional effective approaches for district energy sharing systems in subtropical regions.

Coordinated multi-criteria framework for cycling aging-based battery storage management strategies for positive building–vehicle system with renewable depreciation: Life-cycle based techno-economic feasibility study

The battery-protective control strategy, vehicle-to-building (V2B) interactions, and economic policy regarding grid feed-in tariff are promising techniques for enhancing the lifecycle-based techno-economic performance. However, the current literature indicates limited progress in the techno-economic feasibility of positive building–vehicle systems, with considerations on battery cycling aging, degradation of hybrid renewable generations, and dynamic grid-responsive control strategy. In this study, an interactive building–vehicle system was mathematically formulated with multidirectional energy interaction paradigms, such as building-to-vehicle, grid-to-building, building-to-grid, and grid-to-vehicle. The roles of the V2B interaction levels, grid feed-in schemes, and energy management strategies in techno-economic performances were quantitatively characterised, from the perspectives of the net present value (NPV), discounted payback time (DPT), and net direct energy consumption. Novel energy management strategies were proposed for battery relative capacity improvement in response to the dynamic renewable-demand signal and grid information. Furthermore, uncertainty and sensitivity analyses were performed on the renewable system cost, battery cost, interest rate, and escalation rate of the electricity price. The results indicated that the ignorance of battery cycling aging results in an overestimation on NPV from 2.404 × 108 (0.310 × 108 US$) to 3.005 × 108 HK$ (0.388 × 108 US$). Furthermore, compared to traditional rough estimation on battery aging (with the NPV at 2.446 × 108 HK$ and the DPT at 4 years), the dynamic model in this study can provide more accurate and reliable battery relative capacity, together with conservative assessment on techno-economic feasibility (the NPV at 1.860 × 108 HK$ (0.240 × 108 US$) and the DPT at 5 years). In comparison with the grid feed-in tariff policies in most European countries, the implementation of the latest grid feed-in tariff in Hong Kong can increase the NPV from −7.633 × 107 (−0.985 × 108 US$) to 2.303 × 108 HK$ (0.297 × 108 US$) for the positive building–vehicle system. An interactive building–vehicle system was formulated, together with advanced management strategies for lifecycle-based techno-economic performance enhancement. Comparative analyses among scenarios with different control strategies, V2B interaction levels, and grid feed-in tariff schemes were performed to verify the reliability of the proposed technique for positive building–vehicle systems.

The economic viability of photovoltaic systems in public buildings: Evidence from Italy

Abstract Photovoltaic (PV) systems transform solar irradiation into electricity, thereby substituting for traditional energy sources and reducing environmental pollution. The present work evaluates a developed market (Italy) in which subsidies have been re-introduced for PV plants with a nominal capacity above 20 kW through the FER1 (renewable energy sources) Decree. The discounted cash flow (DCF) methodology is applied to several cases of PV plants in public buildings, in order to determine the value of several critical variables (i.e. level of insolation, plant size, share of self-consumption, investment cost, electricity purchase price). In particular, differences in net present value (NPV) and discounted payback time (DPBT) between subsidy and no-subsidy scenarios are quantified. Break-even point (BEP) analysis is used to define the share of self-consumed energy for which NPV is positive. This share is found to range from 9 to 28% in 105 kW plants and from 10 to 35% in 25 kW plants. In addition, the results verify profitability in almost all of the baseline case studies and only half of the alternative scenarios (involving no subsidies). The estimated profits are consistent with investments aimed at increasing the share of self-consumed energy.