Spark spread – A screening parameter for combined heating and power systems

Combined heating and power (CHP) systems may be considered for installation if they produce savings over conventional systems with separate heating and power. For a CHP system with a natural gas engine as the prime mover, the difference between the price of natural gas and the price of purchased electricity, called spark spread, is an indicator as to whether a CHP system might be considered or not. The objective of this paper is to develop a detailed model, based on the spark spread, that compares the electrical energy and heat energy produced by a CHP system against the same amounts of energy produced by a traditional, or separate heating and power (SHP) system that purchases electricity from the grid. An expression for the spark spread based on the cost of the fuel and some of the CHP system efficiencies is presented in this paper as well as an expression for the payback period for a given capital cost and spark spread. The developed expressions allow determining the required spark spread for a CHP system to produce a net operational savings over the SHP in terms of the performance of system components. Results indicate that the spark spread which might indicate favorable payback varies based on the efficiencies of the CHP system components and the desired payback period. In addition, a new expression for calculating the payback period for a CHP system based on the CHP system capital cost per unit of power output and fuel cost is proposed.     

Planning versus implementation of energy-saving projects by industrial companies. Insights from the Dutch Long-Term Agreements

Companies participating in the Dutch voluntary agreements on energy efficiency are required to announce the energy-saving projects that they have planned for a specified reporting period in an Energy Efficiency Plan (EEP). All projects with a payback period less than 5 years should be implemented. The aim of this paper is to provide insight into the differences in planning and implementation of energy efficiency investments by companies. This analysis is based on the EEPs submitted in the period 2009–2012. By comparing the characteristics of projects that have been implemented with those that were planned, insight is gained in the adjustments that companies make in their energy efficiency investment plans. We look at external circumstances that could explain these adjustments. Our results show that over 12,000 projects have been planned by the 904 long-term agreement (LTA) participants, about half of which are planned ‘certain’, which means that companies are certain that these projects will be implemented. However, we find a large difference between the planned and realised savings of companies and a huge variation in the payback period of both planned and implemented projects. We do not find a correlation between implementation rate and payback period. This suggests that the payback period in the EEPs was not assessed properly or that other than economic motives are more decisive for investment decisions. Our results can be used to improve the effectiveness and efficiency of voluntary agreements.     

A support strategy for the promotion of photovoltaic uses for residential houses in Korea

Various policies such as feed-in tariffs, quota obligations and capital subsides were enacted to expand the uses of renewable energy (RE) in many countries. This study examined whether capital subsidies are cost effective in relation to the installation of solar photovoltaic (PV) facility. To do this, the capacity factor, which is one of the crucial factors for determining the unit cost of electricity from a solar PV system, was estimated from the monthly average clearness index data collected at various cities in Korea. Thermoeconomic analysis was applied to calculate the unit cost of electricity based on the calculated capacity factor of the solar PV system. Instead of subsidizing the same percent of the capital cost of each PV system installation, it is reasonable for the government to adopt a measure to match the subsidy paid to the payback period of the initial investment for all 5 million potential solar PV users in Korea.     

A large-panel unglazed roof-integrated liquid solar collector––energy and economic evaluation

Building-integrated unglazed solar collectors are cost effective solar devices that are suitable for various low temperature applications. In this article we present the design and the parametric analyses of the efficiency of a large-panel unglazed roof-integrated liquid solar collector and an economic evaluation of a large-panel solar-heating system for a swimming pool that is installed at a tourist facility on the Adriatic coast. The design of the solar collector is based on standard metal roofing; it takes into account the technological limitations of prefabricated panels, which makes the serial manufacturing of solar collectors possible. The parametric analyses of the large-panel solar collector’s efficiency were made using the finite-volume numerical method. The numerical model was verified with outdoor measurements, according to the ISO 9806 standard. The efficiency was analysed for the most important parameters: the fin length; the absorber material and thickness; the water mass flow rate; and the wind speed. A solar absorptance of 0.85 was considered in the analyses because this is the value that corresponds to the most frequently used roofing colour. The results show that the efficiency of the analysed panels at T_in=T_a is in the range between 0.26 and 0.74, and the heat loss factors are 2.9–7.9 under no-wind conditions. An economic evaluation using the payback period method was used to select the optimum design for the developed panels on the basis of equal solar gains and the known or estimated initial and operating costs. It was found that for the optimum panel design the payback period is between 1.5 and 2.7 years, based on the current price for non-renewable energy sources. The payback period for presented solar systems is up to four times shorter than for a glazed solar collector system.     

Introducing very large scale PV systems in Israel

The paper introduces the discussion about possible application of very large scale PV systems in Israel. An application of very large scale PV production units of 100 and 500 MW, similar to the unit size of a conventional power station is proposed. A comparative evaluation between conventional power stations and PV stations is carried out in relation to the issues of: geographical location, fuel, pollution, sustainability, availability, watt construction cost and operational characteristics. Calculated payback shows that it decreases from 19 years in 2003 to about 4 years in 2020. Based on worldwide experience of the western countries it is recommended that the country should establish a national program to support the development of PV production and applications.     

Methodology for the design optimisation and the economic analysis of grid-connected photovoltaic systems

In this study, a methodology for the design optimisation and the economic analysis of photovoltaic grid-connected systems (PVGCSs) is presented. The purpose of the proposed methodology is to suggest, among a list of commercially available system devices, the optimal number and type of system devices and the optimal values of the photovoltaic (PV) module installation details, such that the total net economic benefit achieved during the system operational lifetime period is maximised. The decision variables included in the optimisation process are the optimal number and type of the PV modules and the DC/AC converters, the PV modules optimal tilt angle, the optimal arrangement of the PV modules within the available installation area and the optimal distribution of the PV modules among the DC/AC converters. The economic viability of the resulting PVGCS configuration is explored according to the net present value, the discounted payback period and the internal rate of return methods. The proposed method has been applied for the optimal design of a PVGCS interconnected to the electric network of an island with significant solar irradiation potential and the corresponding optimal sizing and economic analysis results are presented.     

偏远岛礁可再生能源开发利用技术经济分析

为了优化偏远岛礁能源保障模式,通过分析柴油发电和可再生能源发电的分项费用特点,分别建立了这两种发电模式的费用表达式,并给出了可再生能源发电投资回收期和寿命期内节省费用的计算公式。以南海岛礁为例分析了太阳能和风能资源状况、柴油运输费用特点,以示例的形式探讨了光伏设备投资回收期与运输费用之间的关系,以及节省费用数额与运行时间之间的关系。研究表明,在偏远岛礁开发利用太阳能和风能资源在经济上具有可行性;岛礁距离越远,可再生能源设备投资回收期越短,节省的费用越多;在南海岛礁光伏发电设备投资回收期一般不超过8 a。     

Performance evaluation of photovoltaic–thermosyphon system for subtropical climate application

The rapid development and sales volume of photovoltaic (PV) modules has created a promising business environment in the foreseeable future. However, the current electricity cost from PV is still several times higher than from the conventional power generation. One way to shorten the payback period is to bring in the hybrid photovoltaic–thermal (PVT) technology, which multiplies the energy outputs from the same collector surface area. In this paper, the performance evaluation of a new water-type PVT collector system is presented. The thermal collection making use of the thermosyphon principle eliminates the expense of pumping power. Experimental rigs were successfully built. A dynamic simulation model of the PVT collector system was developed and validated by the experimental measurements, together with two other similar models developed for PV module and solar hot-water collector. These were then used to predict the energy outputs and the payback periods for their applications in the subtropical climate, with Hong Kong as an example. The numerical results show that a payback period of 12 year for the PVT collector system is comparable to the side-by-side system, and is much shorter than the plain PV application. This is a great encouragement in marketing the PVT technology.     

The use of CHP and absorption cooling in cold storage

In recent years, it has become standard practice to consider combined heat and power (CHP) systems early in the design stage of commercial buildings. With new initiatives from the UK government on reduced energy use, energy efficient systems such as CHP have been considered for a wider application particularly within industrial building design. The viability of CHP in a typical cold storage application is described in this paper. The electrical energy and heating requirements are defined and used to assess the annual energy consumption of a traditional cold storage design using a thermal model. The analysis is then used to consider the economics of different CHP configurations, which includes an integrated CHP and absorption system used to provide chilled glycol for the cold storage facilities. The additional capital cost of each configuration is shown and this is used to calculate the payback period. The results show that an attractive payback period of approximately four years for a combined CHP and absorption system may be achieved.     

Implementation of energy efficiency projects by Dutch industry

As potentials for energy savings are huge, industry can provide a major contribution to energy savings goals. This paper focuses on the energy savings realized under the Dutch voluntary agreements in the period 2001–2011. Participants in these schemes are obliged to plan and implement all measures with a payback period of less than 5 years. This paper shows how many of these projects have been implemented and how much savings they generate. Our findings show that large differences exist in the realized savings between individual companies. There is however no significant difference in savings observed between companies that participate in the Emission Trading System (ETS) and companies that do not. Although it is impossible to disentangle the drivers behind the implementation of these projects, the amount of savings suggest that at least part of them was implemented because of different energy policy instruments.     

Investigating the possibility of using different hub height wind turbines in a wind farm

Many researchers have focused on the layout design of a wind farm using the computational methods. Most of previous researches focused on relevant large cell size and using same hub height wind turbines. In this paper, the authors investigate the possibility of using different hub height wind turbines in a wind farm. A limited area (2?km?×?2?km) with constant wind speed and direction is considered as the potential wind farm area, and a nested genetic algorithm is used as optimisation algorithm. Two different hub height wind turbines are introduced with two different cell sizes. Power output, cost, payback period, and total profit are selected as evaluation criteria when comparing the layouts with same hub height wind turbines with the layouts with different hub height wind turbines. The results demonstrate that it is feasible and possible to use different hub height wind turbines in a wind farm.     

节能成本分析法在节能技术评价中的应用

节能技术经济性评价是节能技术选择的重要依据。传统的评价指标,如投资回收期、内部收益率、净现值等指标是基于现金流计算得出,而现金流的计算与项目所在地的能源价格紧密相关。由于各地能源价格的差异,同一类项目的上述指标因地而异,因此,采用以上指标对节能技术的评价不具备普遍适用性。本文介绍了一种不受项目所在地能源价格影响,并具有普遍适用性的指标——节能成本,并以案例说明。     

基于层次分析法的太阳能利用技术综合评价

本文首先利用一个非稳态传热模型对同一环境条件下光伏光热一体化（PV/T）系统、光伏系统（PV）和太阳能热水器的能效进行分析,然后采用层次分析法（AHP）对不同品质终端能源输出的太阳能利用系统的能效统一表征,并以北京、广州和银川为代表的不同城市自然环境及用电价格为条件的三种情景,对三种太阳能利用系统的综合能源利用效率、累计净收益和投资回收期进行分析。结果表明,太阳能利用系统的经济性不仅受到系统能源利用效率和成本的影响,系统所在地的自然环境和电价水平也会引起系统经济性发生变化,因此考虑多种因素的综合评价可以为太阳能技术推广提供更客观和准确的参考。     

Experimental investigation of a new solar desalination prototype using the humidification dehumidification principle

This paper tackles an experimental investigation of a new solar desalination prototype using the humidification dehumidification principle at the weather conditions of Sfax City, Tunisia. The prototype is designed and constructed at the national engineering school of Sfax to conduct this experimental investigation under different meteorological and operating parameters. It is composed of a flat plate solar air collector, a flat plate solar water collector, a humidifier, an evaporation tower and a condensation tower. An economic analysis was conducted, since it affects the final cost of produced water, to determine both the cost of fresh water production and the payback period of the experimental setup. Although a system may be technically very efficient, it may not be economic. The experimental investigation of the dynamic behaviour of the solar desalination unit during summer season (June, July and August) and during a typical day in July was carried to study the temporal evolutions of the temperature of air and water and the relative humidity at the inlet and the outlet of each component of the system.     

Techno-economical assessment of grid connected PV/T using nanoparticles and water as base-fluid systems in Malaysia

In this study, the techno-economic assessment of GCPVT with nanofluid has been investigated based on theoretical and experimental work in Malaysia. The productivity and utilisation of the PV have been investigated using yield and capacity factors (CFs), respectively. Also, the cost of energy and payback period has been calculated. The system installed, tested, and data have been collected. Evaluation of the system in terms of current, voltage, power and efficiency are presented. The average daily ambient temperature and total global solar energy in Kuala Lumpur are 38.89°C and 4062?Wh/m², respectively. MATLAB software is used to analyse the measured data. The assessment results show that the GCPVT system has annual yield factor, CF, the cost of energy; payback period, and efficiency are (128.34–183.75)?kWh/kWp, (17.82–25.52)%, 0.196?USD/kWh, 7–8 years and 9.1%, respectively. This study indicates that the GCPVT system with nanofluid improved the PV technical and economic performance.     

Economic evaluation of a solar water heating system

This paper describes different methods of analysis of a solar water heating system to determine its economic viability. The solar fraction, required for this analysis, has been calculated with a stimulation program using hourly meteorological data of Singapore. A measured load profile, representing the average condition, was used for this program. The economic variables have been selected from the trends shown in previous years.When different economic optimization criteria were applied to the CIAS solar system, it was seen that both the life cycle saving and the annualized life cycle cost lead to the prediction of the same optimum collector area of 1200 m². The payback period and the internal rate of return analyses also predicted the same optimum collector area of 1000 m², which is smaller than that predicted by the method of life cycle costing. For the economic variables used in this analysis, the minimum payback period is about 14 years.     

Examining the cost efficiency of Chinese hydroelectric companies using a finite mixture model

This paper evaluates the operational activities of Chinese hydroelectric power companies over the period 2000–2010 using a finite mixture model that controls for unobserved heterogeneity. In so doing, a stochastic frontier latent class model, which allows for the existence of different technologies, is adopted to estimate cost frontiers. This procedure not only enables us to identify different groups among the hydro-power companies analysed, but also permits the analysis of their cost efficiency. The main result is that three groups are identified in the sample, each equipped with different technologies, suggesting that distinct business strategies need to be adapted to the characteristics of China's hydro-power companies. Some managerial implications are developed.     

The internal rate of return of photovoltaic grid-connected systems: A comprehensive sensitivity analysis

At present, photovoltaic grid-connected systems (PVGCS) are experiencing a formidable market growth. This is mainly due to a continuous downward trend in PV cost together with some government support programmes launched by many developed countries. However, government bodies and prospective owners/investors are concerned with how changes in existing economic factors – financial incentives and main economic parameters of the PVGCS – that configure a given scenario may affect the profitability of the investment in these systems. Consequently, not only is a mere estimate of the economic profitability in a specific moment required, but also how this profitability may vary according to changes in the existing scenario. In order to enlighten decision-makers and prospective owners/investors of PVGCS, a sensitivity analysis of the internal rate of return (IRR) to some economic factors has been carried out. Three different scenarios have been assumed to represent the three top geographical markets for PV: the Euro area, the USA and Japan. The results obtained in this analysis provide clear evidence that annual loan interest, normalised initial investment subsidy, normalised annual PV electricity yield, PV electricity unitary price and normalised initial investment are ordered from the lowest to the highest impact on the IRR. A short and broad analysis concerning the taxation impact is also provided.     

Capital cost and economic viability of thermosyphonic solar water heaters manufactured from alternate materials in India

Many companies in India manufacture solar water heaters but these are not becoming popular in the domestic sector because of their high cost. The Ministry of Non-Conventional Energy Sources (MNES), New Delhi is recommending flat-plate collectors with copper (Cu) risers, headers and plate. Therefore, their cost is high. Long term studies have been carried out at the Central Arid Zone Research Institute, Jodhpur, to reduce the cost by replacing copper tubes with galvanised steel (G.S.) tube and copper plate with aluminium (Al) plate. The aluminium plate is wrapped over the G.S. tube by a special wire wound technique so that good contact of plate with risers and headers has been maintained. In this paper performance and testing of solar water heaters having G.S.–Al fin, Cu–Al fin and Cu–Cu fin in flat-plate collectors have been compared. It has been found that performance of all the three heaters is almost similar. The heater can provide 100 litres of hot water at an average temperature 62.0°C at 4 pm that can be retained to 50.4°C when average tap water temperature was 23.9°C. The efficiency of the heater is 51.9%. The cost of the heater with G.S.–Al collector is only Rs. 8,000.00 while it is Rs. 10,250.00 for solar water heaters with Cu–Cu collectors. The payback period of a solar water heater with G.S.–Al collector has been worked out by considering 10% compound annual interest, 5% maintenance cost, 5%, inflation in fuel prices and maintenance cost. The payback period varies between 2.92 years to 4.53 years depending upon which fuel it replaces. The payback periods are in increasing order with respect to fuels: electricity, firewood, LPG, charcoal, and kerosene.     

Economic optimization and sensitivity analysis of photovoltaic system in residential buildings

This paper deals with the problem of optimal size of grid-connected photovoltaic (PV) system for residential application. It is assumed the PV system can input or output liberally the electricity to the utility electricity grid. A simple linear programming model is developed. The objective is to minimize the annual energy cost of a given customer, including PV investment cost, maintenance cost, utility electricity cost, subtracting the revenue from selling the excess electricity. The model reports the optimal PV capacity that customers adopt with their electricity requirements. Using this model, an investigation is conducted of economically optimal PV investment under several conditions for a typical residential building. Additionally, the sensitivity of levelized cost and simple payback period to various economic and technical circumstances has been analyzed.