Energy efficiency improvement of dryer section heat recovery systems in paper machines – A case study

Modern paper machines are equipped with heat recovery systems that transfer heat from the humid exhaust air of the paper machine’s dryer section to different process streams. As a result of process changes, the heat recovery systems may operate in conditions far from the original design point, creating a significant potential for energy efficiency improvement. In this paper we demonstrate this potential with a case study of three operating paper machines. Both operational and structural improvement opportunities are examined. Since the existing retrofit methodologies for heat exchanger networks can not be applied to cases with condensing air, we use thermodynamic simulation models presented earlier to assess the effects of possible changes on the existing heat recovery systems. In order to reduce the required processing time of the simulation models, only a limited number of pre-screened retrofit designs are considered. The pre-screening is carried out on the basis of guidelines presented earlier. The analysis in the case mill revealed savings of 110 GWh/a in process heat with profitable investments. According to the follow-up study, the investments carried out have resulted in 12% lower fuel use and 24% lower CO₂ emissions. The results imply that all operating paper machines should be similarly examined.     

Feasibility study for the installation of HVAC for a spa by means of energy recovery from thermal water—Part II: Energy analysis

The use of a low temperature geothermal spring together with the heat energy still contained in waste water from the different therapy systems installed in a spa (shower, jets, bathrooms, jacuzzis, pools, ventilation processes) can significantly reduce the operating and maintenance costs of the installation. This covers part of the air conditioning needs of the building and of the heating of thermal water to the appropriate temperature for therapeutic use.In the first part of the study, an analysis of the spring's situation was made, calculating the thermal water needs and presenting the consumption according to the operation schedule on different types of day. In this way, the contribution the spring was capable of giving was compared and the evolution of the thermal water in the tanks was studied. In the second part, the climatic conditions that the spa should meet are studied, along with the loads that it should support, the energy reclaimed from the different heat focuses and the repercussions on the final solution.     

Energy efficiency in social housing: Opportunities and barriers from a case study in Brazil

This paper investigates the energy efficiency in a segment of the building sector in emerging countries by analyzing and evaluating the energy efficiency of a social housing project in Brazil. Energy efficiency measures and bioclimatic design strategies are developed in order to improve thermal comfort in this social housing project and to reduce the energy consumption and expenses of their residents. The institutional barriers and constraints toward higher efficiency are described. The results of this study show that there is a high potential to increase energy efficiency in social housing in emerging countries like Brazil. The implementation and consideration of the energy efficiency measures and policy recommendations would contribute substantially to the goal to dampen the fast growth of energy demand in these countries. Moreover the improvement of energy efficiency in the social housing sector could be a driver for market transformation towards more sustainability in the whole building sector.     

Impact of European standard EN15251 in the energy certification of services buildings—A Portuguese study case

In Europe, about 40% of the energy is consumed in buildings, more than by industry or transport. However, there is a great potential for energy savings in this field, often at little cost. A new European directive and several European standards, including the comfort standard EN15251, were created to develop comfortable and efficient buildings.     

Development of energy efficiency improvement in the Tunisian hotel sector: a case study

Tunisia expects a very large growth in energy demand but Tunisian' indigenous energy resources are limited. Today Tunisian' energy resources meet the total primary energy demand. In short time Tunisia will become an importer country for primary energy.Energy consumption and conservation in Tunisia has received growing attention in recent years. This paper presents the results and analysis from the data collected during the energy audits of a hotel unit located in the center of Tunis during the years 1987, 1996 and 2002. Two energy conservation measures were carried out to investigate the energy savings after two energy audits. The objective was to obtain a quantified energy saved from the effects of efficient technologies.Based on the findings presented in this paper it is suggested there exists significant energy savings potentials for the Tunisian hotel industry.     

Heat planning for fossil-fuel-free district heating areas with extensive end-use heat savings: A case study of the Copenhagen district heating area in Denmark

The Danish government plans to make the Danish energy system to be completely free of fossil fuels by 2050 and that by 2035 the energy supply for buildings and electricity should be entirely based on renewable energy sources. To become independent from fossil fuels, it is necessary to reduce the energy consumption of the existing building stock, increase energy efficiency, and convert the present heat supply from fossil fuels to renewable energy sources. District heating is a sustainable way of providing space heating and domestic hot water to buildings in densely populated areas. This paper is a theoretical investigation of the district heating system in the Copenhagen area, in which heat conservation is related to the heat supply in buildings from an economic perspective. Supplying the existing building stock from low-temperature energy resources, e.g. geothermal heat, might lead to oversized heating plants that are too expensive to build in comparison with the potential energy savings in buildings. Long-term strategies for the existing building stock must ensure that costs are minimized and that investments in energy savings and new heating capacity are optimized and carried out at the right time.     

Efficiency of and interference among multiple Aquifer Thermal Energy Storage systems; A Dutch case study

This paper describes the analysis of a real case of multiple Aquifer Thermal Energy Storage systems. The Hague, the capital city of the province of South Holland in the Netherlands, is densely populated with many ATES systems. A total of 19 ATES systems are installed in an area of 3.8 km² with a total of 76 functioning wells. The analysis focuses on the development of a coupled groundwater flow and heat transfer model over a period of 10 years. Results are then post-processed to evaluate efficiency of each individual well and system. Efficiency of the ATES systems has ranged between 68% and 87%. The analysis showed that efficiency tends, in general, to increase over time and stabilize at an asymptotic value after few years. Analysis of interference among individual wells of an ATES system and wells of other systems showed that interference could, in fact, have a positive impact on the efficiency of a well/system. Interference can increase efficiency of an ATES system since it can help in trapping energy (cold or warm) within the capture zone of all operating ATES systems. In the study area, the interference phenomenon affects efficiency, in general, positively where it increases the efficiency of individually operating wells by a maximum of 20%. However, the phenomenon also affects efficiency of some wells negatively where it reduces the efficiency of individually operating wells by a maximum of 25%. In average, systems in the study area are positively affected by interferences among each other with an overall average of 3.2% for all wells (over the 10 years operation period).     

Analysis of energy efficiency and carbon dioxide reduction in the Chinese pulp and paper industry

Pulp and paper production, an energy-intensive process, is among the main light industries contributing to energy saving and pollution emission reduction in China. The improvement of energy efficiency is essential for energy consumption and sustainable development. This study analyzes the negative factors in the pulp and paper sector by calculating energy efficiency from the lengthways time and investigating the gap between China and foreign countries through a horizontal comparison. Accordingly, energy efficiency has increased in the Chinese pulp and paper industry with years of efforts, but its transformation remains unclear. Furthermore, the energy-saving potential, energy cost saving, and carbon dioxide emission reduction in the pulp and paper industry are evaluated according to the Twelfth Five-year Plan (2011–2015). The results show that the pulp and paper industry has further capabilities for energy-saving and carbon dioxide emission reduction by improving energy efficiency in China, resulting in great economic benefit. In brief, new technology and energy structure adjustment are long-term strategies for energy conversation, with changes in the scale of mills expected to provide huge opportunities to improve energy efficiency in China within a short period.     

Energy efficient and sustainable ancient museum buildings: a case study in Florence

The Historical Bardini Museum in Florence is a representative paradigm of the Italian Museum Building, and it is very suitable to serve as an exemplary pilot project for the restoration of historical museums. This article presents results of the architectural and energy retrofitting carried out applying appropriate and strategic low-energy and sustainable techniques and of the monitoring campaign (IAQ, thermal comfort, light, acoustic) performed first to evaluate the existing situation and then to verify comfort parameters and the energy consumption after works. The Bardini Museum participates, as Italian case study, to the European MUSEUMS project, financed by EU Commission in the Fifth Framework Programme. The result of this project is to provide also with a direct guidance, complete with architectural and engineering examples, for design professionals and museum authorities, setting a new standard for energy consumption in museum buildings. In parallel, it has aimed to disseminate effective information for designers and local authorities and to demonstrate the efficiency of the measures in order to promote them in efficient market promotion, penetration and utilization.     

Energy,exergy and exergoeconomic analysis of a steam power plant: A case study

The objective of this paper is to perform the energy, exergy and exergoeconomic analysis for the Hamedan steam power plant. In the first part of the paper, the exergy destruction and exergy loss of each component of this power plant is estimated. Moreover, the effects of the load variations and ambient temperature are calculated in order to obtain a good insight into this analysis. The exergy efficiencies of the boiler, turbine, pump, heaters and the condenser are estimated at different ambient temperatures. The results show that energy losses have mainly occurred in the condenser where 306.9 MW is lost to the environment while only 67.63 MW has been lost from the boiler. Nevertheless, the irreversibility rate of the boiler is higher than the irreversibility rates of the other components. It is due to the fact that the combustion reaction and its high temperature are the most significant sources of exergy destruction in the boiler system, which can be reduced by preheating the combustion air and reducing the air–fuel ratio. When the ambient temperature is increased from 5 to 24°C, the irreversibility rate of the boiler, turbine, feed water heaters, pumps and the total irreversibility rate of the plant are increased. In addition, as the load varies from 125 to 250 MW (i.e. full load) the exergy efficiency of the boiler and turbine, condenser and heaters are increased due to the fact that the power plant is designed for the full load. In the second part of the paper, the exergoeconomic analysis is done for each component of the power plant in order to calculate the cost of exergy destruction. The results show that the boiler has the highest cost of exergy destruction. In addition, an optimization procedure is developed for that power plant. The results show that by considering the decision variables, the cost of exergy destruction and purchase can be decreased by almost 17.11%. Copyright © 2008 John Wiley & Sons, Ltd.     

From fluid milk to milk powder: Energy use and energy efficiency in the European dairy industry

In this paper, we conduct a cross-country analysis of energy consumption and energy efficiency for the dairy industry in four European countries. Changes in energy efficiency were monitored in two different ways. One way is to look at the energy use by tonne of milk processed by dairies (EE_Ip1$\mathit{EE}{I}_{p1}$). Another way is by comparing the actual energy use with the energy that would have been used if no changes in energy efficiency would have taken place (EE_Ip2$\mathit{EE}{I}_{p2}$). A characteristic of EE_Ip2$\mathit{EE}{I}_{p2}$ is that it corrects for differences in product mix among countries and in time. We found that changes in production mix are important in three of the four countries studied and that EE_Ip2$\mathit{EE}{I}_{p2}$ should be preferred when comparing levels of energy efficiency among countries or when there are significant changes in product mix. Once changes in product mix have been taken into account, our results show that France, Germany, the Netherlands and the United Kingdom have reduced their values in EE_Ip2$\mathit{EE}{I}_{p2}$, respectively by −0.4%, −2.1%, −1.2% and −3.8% per annum. The results also show that the British, German and Dutch dairy industries have converged towards similar (lower) values in their energy efficiency indicators and that the French dairy industry would save 30% if were to converge to similar values of EE_Ip$\mathit{EE}{I}_p$ as the ones obtained for Germany or the United Kingdom.     

Hybrid solution and pump-storage optimization in water supply system efficiency: A case study

Environmental targets and saving energy have become ones of the world main concerns over the last years and it will increase and become more important in a near future. The world population growth rate is the major factor contributing for the increase in global pollution and energy and water consumption. In 2005, the world population was approximately 6.5 billion and this number is expected to reach 9 billion by 2050 [United Nations, 2008. www.un.org, accessed on July]. Water supply systems use energy for pumping water, so new strategies must be developed and implemented in order to reduce this consumption. In addition, if there is excess of hydraulic energy in a water system, some type of water power generation can be implemented.     

Energy in subsistence agriculture: A case study of nepal

The paper examines the total energy input requirements and outputs of subsistence agriculture in the rural areas of Nepal with specific emphasis on animate energy inputs for different crops. It analyses the availability of animate energy and the usage pattern and also looks into various issues of energy demands in subsistence agriculture at micro levels and its impact at macro level. The paper attempts to highlight major policy options that are imperative for raising the living standard of the rurals through increased productivity.     

Improving the institutional structures for disseminating energy efficiency in emerging nations: a case study for energy agencies in South Africa

Emerging nations are typically characterised by highenergy intensities despite significant energy efficiency potentials and numerous project oriented efforts to introduce energy-efficient technologies. The paper argues that successful technology dissemination needs appropriate institutional structures to reduce the related transaction cost. While a project-by-project approach risks to evaporate after completion, an energy agency would allow to bundle the know-how and information gained, ease access to funding and thus reduce information search cost and increase availability of efficient technologies. In a case study for South Africa, we examine the appropriateness of this concept for emerging nations. We discuss the underlying incentive problem from a new institutional economics perspective and suggest an approach to the design and implementation of operable energy agencies.     

Energy saving and emission reduction: A project of coal-resource integration in Shanxi Province,China

The small or middle coal mines with illegal operations in developing countries or regions can cause bad energy waste and environmental disruption. The project of coal-resource integration in Shanxi Province of China gives a new idea or an approach to energy saving and emission reduction. It is a social- and economic-ecological project. The paper shows the targets of energy saving and emission reduction in Shanxi Province, and analyses the aims, significance, design process and implementation of the integration project. Based on that, the paper discusses the challenges and opportunities the project brings. The analysis shows that the project of coal-resource integration in developing countries or regions can effectively improve mining technologies, collect capital and impel international cooperation and exchange. Finally, the paper analyses the concerns about the future, including the possible problems of implementation period, industrial updating, environmental impact and re-employment. However, the successful integration of coal resources can mitigate energy crisis and climate crisis and promote cleaner production effectively.     

Energy intensity and greenhouse gases footprint of metallurgical processes: A continuous steelmaking case study

The demand on primary energy resources of three steelmaking technologies has been evaluated using an integrated energy analysis approach that takes into account the energy equivalent of major materials and supplies used in the process, as well as the inefficiency of electricity generation. Two new parameters, Material CO₂ Footprint (MCF) and Process CO₂ Footprint (PCF), are defined to provide unified measures for carbon footprint of the treated materials, and the process respectively. Using these measures, a comparative study of the three processes has been performed. It is demonstrated that a novel steelmaking technology that operates continuously leads to substantial reduction in the overall energy demand, when compared with the conventional batch processes. CO₂ reduction associated with the improvement of the energy efficiency is presented for several scenarios of power generation.     

Energy efficiency as a credence good: A review of informational barriers to energy savings in the building sector

Information problems have early been suspected to be the main barrier to energy-efficiency investment. I review the vast yet piecemeal research that has been carried out since. Focusing on energy efficiency in buildings, I organize the review around the concept of credence good: just like that of auto repairs or taxi rides, the quality of energy-efficiency measures is never fully revealed to the buyer; as a result, it is subject to multiple information asymmetries. My first contribution is to distinguish symmetric-information problems from information asymmetries. The former arise when information is either incomplete or imperfect, but equally shared by contracting parties; as non-market failures, these can be addressed by technological progress and insurance markets. My second contribution is to give structure to the information asymmetries associated with energy efficiency by disentangling screening, signalling, moral hazard and price discrimination within a variety of contractual relationships involving buyers and sellers, owners and renters, borrowers and lenders, and regulators and policy stakeholders. I find evidence of information asymmetries to be compelling in utility-included rental contracts, unclear in home sales and rentals, and scarce in retrofit contracting and financing. I conclude by discussing the intricacies between informational and behavioural problems in energy-efficiency decisions.     

Key issues in the microchemical systems-based methanol fuel processor: Energy density,thermal integration,and heat loss mechanisms

Microreactor technology is a promising approach in harnessing the high energy density of hydrocarbons and is being used to produce hydrogen-rich gases by reforming of methanol and other liquid hydrocarbons. However, on-demand H₂ generation for miniature proton exchange membrane fuel cell (PEMFC) systems has been a bottleneck problem, which has limited the development and demonstration of the PEMFC for high-performance portable power. A number of crucial challenges exist for the realization of practical portable fuel processors. Among these, the management of heat in a compact format is perhaps the most crucial challenge for portable fuel processors. In this study, a silicon microreactor-based catalytic methanol steam reforming reactor was designed, fabricated, and demonstrated in the context of complete thermal integration to understand this critical issue and develop a knowledge base required to rationally design and integrate the microchemical components of a fuel processor. Detailed thermal and reaction experiments were carried out to demonstrate the potential of microreactor-based on-demand H₂ generation. Based on thermal characterization experiments, the heat loss mechanisms and effective convective heat coefficients from the planar microreactor structure were determined and suggestions were made for scale up and implementation of packaging schemes to reduce different modes of heat losses.     

Current and future financial competitiveness of electricity and heat from energy crops: A case study from Ireland

It has been demonstrated that Miscanthus and willow energy-crop cultivation could be economically competitive with current agricultural land uses at a farm-gate biomass price ranging from €70 to €130 t⁻¹ dry matter [Styles, D., Thorne, F., Jones, M.B., in review. Energy crops in Ireland: An economic comparison of willow and Miscanthus production with conventional farming systems. Biomass and Bioenergy, May 2006]. This paper uses the same farm-gate prices to calculate the economic competitiveness of energy crop electricity and heat production, using a net-present-value (NPV) approach (20-year period, 5% discount rate). Direct and gasified co-firing of willow wood with coal would result in electricity generation 30% or 37% more expensive than coal generation, at current coal and CO₂ allowance prices and a farm-gate biomass cost of €100 t⁻¹. ‘Break-even’ CO₂ allowance prices are €33 and €37 t⁻¹, respectively. However, co-firing of Miscanthus with peat is close to economic competitiveness, and would require a CO₂ allowance price of €16 t⁻¹ to break-even (against a current price of €12 t⁻¹). NPV analyses indicate that wood heat is significantly cheaper than oil, gas or electric heat, excluding existing wood-boiler installation subsidies. Discounted annual savings range from €143 compared with gas to €722 compared with electric heating at the domestic scale and from €3454 to €11,222 at the commercial scale. Inclusion of available subsidies improves the comparative economics of domestic wood heat substantially. The economic advantage of wood heat is robust to variation in fuel prices, discount rates and heat loads. The greatest obstacles to energy-crop utilisation include: (i) a reluctance to consider long-term economics; (ii) possible competition from cheaper sources of biomass; (iii) the need for a spatially coordinated supply and utilisation network.     

Industrial energy efficiency improvement through cogeneration: A case study of the textile industry in Thailand

Natural gas cogeneration presently appears to be a promising alternative to satisfy the energy utility requirement of the process industries thanks to the favorable energy policy of the Government of Thailand. In this paper, we detail a case study in a textile factory where use of gas-turbine cogeneration with a post-combustion heat recovery system is found to be the most suitable solution. This system has not only the highest thermal efficiency, but it can also provide flexibility in operation. Financial analysis of the most suitable cogeneration configuration provides the net present value (NPV), pay-back period (PBP) and internal rate of return (IRR) with values of 310 million Baht, 5.3 years and 26.6%, respectively. The thermal-matching option is not found to be attractive because the sale price of electricity to the state electric utility is not high enough to absorb the additional investment required for the prime mover. Incorporation of an absorption chiller in the cogeneration system does not bring in any additional advantage as there is no excess waste heat available in this factory.