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• Drain water heat recovery potential of commercial kitchens is examined. • Financially feasible potential in the hospitality sector in the UK is 1.24 TWh / yr. • This can be achieved at 2.94 p £/ kg Ce saved , over a 10-year lifetime. • This leads to 344 k tons Ce / yr reduced emissions. • 160 GWh (a reduction of 44 k tons Ce / yr) remains commercially unexploitable. In order to meet ambitious greenhouse gas reduction targets, the reduction of fuel consumption in the heating sector is necessary. This paper assesses the impact of introducing direct drain water heat recovery systems in commercial kitchens in the UK, based on a commercially available heat exchangers. The recoverable heat from these kitchens was estimated using Monte Carlo simulation, sector consumption data, and data measured in the field. A financial criterion, the Net Present Value calculated over 10 years, was used to estimate feasibility threshold values for the kitchen water consumption, varying with the heating fuel used in each premises. This analysis resulted in a total financially feasible potential for drain water heat recovery in the hospitality and food service sector in the UK of approximately 1.24 TWh / yr , leading to a reduction in GHG emissions of 344 k tons Ce / yr. This could be achieved at a cost of approximately 2.94 p £/ kg Ce saved , over a 10-year lifetime, which was several orders of magnitude smaller than traditional renewable heat sources such as heat pumps. Commercially available drain water heat recovery systems could, when installed, exploit around 88% of current potential in drain water heat in commercial kitchens (1.40 TWh / yr) in a manner that is financially profitable. However, this paper assumes the availability of a 2 m vertical drop in the kitchen drain, required to install the heat exchanger, and thus achieve optimal effectiveness. In case this head is not available, the heat recovery potential would be untapped, as in approximately 160 GWh , in kitchens where the hot water consumption is too small for financial profitability. This corresponds to a reduction in GHG emissions of 44 k tons Ce / yr and leaves a gap in the market for inexpensive DWHR devices, which could exploit this potential at lower efficiencies. [ABSTRACT FROM AUTHOR]

Abstract Temporal mismatches between heat provided by a drain water heat recovery system, and heat consumption are, although often disregarded in literature, a crucial factor in assessing the feasibility of the former. Generally, the only available information for residences is the average monthly consumption. The probabilistic method described in this paper uses observations from 113 residences to predict daily and monthly consumption profiles, using monthly consumption as a starting point. These profiles were then used to study the operation of a drain water heat recovery system, but can also be used to assess the operation of other heating methods where the supply is not controlled, such as solar thermal. The operation of the drain water heat recovery systems was predicted based on a monitoring campaign at 3 residences, measuring wastewater temperature and flow at 5-minute intervals, for over a 1-year period. The performance of this system was assessed using the performance data of 26 commercially available heat pumps, with rated power below 7 kW. The method was applied to a theoretical average Irish residence, obtained through a Monte Carlo analysis on just under 700 000 Irish residences. The method highlighted the potential for a reduction in heating related greenhouse gas emissions by 7.6% to 22%. However, this increased heating costs by 120% to 130%. At current traditional heating prices, the DWHR system for a single residence is not financially competitive with traditional systems, due to its significant capital investment. Further research should examine combining waste water streams from different residences to provide a larger flow, and potentially a high recoverable energy volume, thus improving financial viability. Policy makers should also consider incentivizing DWHR to improve its financial competitiveness and help achieve the above GHG emissions savings. [ABSTRACT FROM AUTHOR]

The European Union declared wastewater as a renewable energy source in its Green Deal. To meet these targets, the scientific community has been proposing new technologies to improve energy conversion efficiency of renewable energy powered thermal systems. The present research examines heat recovery from commercial kitchen grease traps (GT) as a means of reducing the net energy requirement of commercial hot water use in food related activities. A GT was integrated with heat recovery unit and is referred to as a hybrid GT system. Two designs of thermal recovery units comprising a planar and rectangular coil type heat exchanger (HX) were assessed individually to compare their thermal recovery capabilities. The planar HX equipped GT was first experimentally investigated and subsequently examined in more detail using 3D numerical analysis. Thermal stratification was observed along the GT depth for which the rectangular HX showed greater potential for thermal recapture from the high temperature kitchen wastewater. The novel rectangular HX design was found to save 2.6 kW of thermal energy in the kitchen GT and was 48% more efficient compared to the planar HX. The proposed GT hybrid design enables more sustainable production of food via a clean auxiliary thermal back-up, reducing greenhouse gases emission released in water heating. Heat recovery from commercial kitchen GTs has been shown in this study to be technically viable with strong potential for economic viability and positive environmental impact through reducing the carbon footprint of water heating. [Display omitted] • Investigated thermo-hydraulic performance of hybrid Grease-Trap device. • Planar and upgraded rectangular thermal recovery unit designs were compared. • Performance discussed in terms of thermal recovery potential and effectiveness. • Proposed design could save up to 40% of the heat embedded in kitchen wastewater. [ABSTRACT FROM AUTHOR]

The number of micro-scale spirit distilleries worldwide has grown considerably over the past decade. With an onus on the distillery sector to reduce its environmental impact, such as carbon emissions, opportunities for increasing energy efficiency need to be implemented. This study explores the potential environmental benefits and financial gains achievable through heat recovery from different process and by-product streams, exemplified for a Scotch whisky distillery, but transferrable to micro-distilleries worldwide. The eco-efficiency methodology is applied, taking into account both climate change and water scarcity impacts as well as economic performance of alcohol production with and without heat recovery. A Life Cycle Assessment, focusing on climate change and water scarcity, is combined with a financial assessment considering investment costs and the present value of the savings over the 20-year service life of the heat recovery system. The proposed heat recovery systems allow carbon emission reductions of 8–23% and water scarcity savings of 13–55% for energy and water provision for 1 L of pure alcohol (LPA). Financial savings are comparatively smaller, at 5–13%, due to discounting of the future savings – but offer a simple payback of the investment costs in under two years. The eco-efficiency of the distillery operations can be improved through all proposed heat recovery configurations, but best results are obtained when heat is recovered from mashing, distillations and by-products altogether. A sensitivity analysis confirmed that the methodology applied here delivers robust results and can help guide other micro-distilleries on whether to invest in heat recovery systems, and/or the heat recovery configuration. Uptake should be enhanced through increased information and planning support, and in cases where the distillery offers insufficient heat and water sinks to use all pre-warmed water, opportunities to link with a heat sink outside the distillery are encouraged. A 10% reduction in heating fuel use through heat recovery has the potential to save 47 kt of CO 2 eq. or £7.4 M per annum in United Kingdom malt whisky production alone, based on current fuel types used and current prices (2021). • Life cycle environmental and financial analysis of heat recovery for distilleries. • Heating fuel can be reduced by 10–25%, water consumption by up to 50%. • Payback on capital expenditure is achievable within 2 years. • Full exploitation of excess heat will often require off-site heat sinks. • Technical and admin support for heat recovery through local governments encouraged. [ABSTRACT FROM AUTHOR]

Although the food service sector is a major user of water, the potential for heat recovery from commercial kitchens' drain water remains largely unexplored. For the first time, we compare the life cycle environmental burdens of producing and installing a heat recovery system with the environmental credits arising from energy savings for a restaurant case study, and for the entire UK food service sector. Life Cycle Assessment was applied to determine the impacts of heat recovery systems made from different materials and comprising a heat exchanger in the shape of a concentric double-walled pipe, pipework and fittings. The design option with the smallest environmental footprint combined a heat exchanger made out of polypropylene-graphite (PP-GR) with polyethylene pipework, exhibiting 80–99% less environmental impact compared with components made out of (35% recycled) copper. Contrasting the environmental impacts of two heat recovery set-ups with energy savings shows that a PP-GR based system pays back all burdens of the seven assessed environmental impact categories, within two years, while payback times for the copper-based system vary depending on the replaced energy source, and can exceed the 10 year operational lifetime of the system. When looking at typical flow-rates in UK food outlets, net environmental savings can be realised across all analysed impact categories above a threshold water consumption of 555 L/day, using current technology. Extrapolation to the UK food service sector indicates annual greenhouse gas emission mitigation potential of about 500 Gg CO 2 equivalent. Image 1 • LCA on equipment for recovering heat from commercial kitchen's drain water. • Heat recovery from kitchen drain water could reduce UK GHG emissions. • Trade-off between climate change mitigation and resource depletion. • Heat exchanger from polypropylene-graphite preferable to copper device. • Full environmental payback achievable from 300 m3 water consumption per year. [ABSTRACT FROM AUTHOR]

To avoid the geographical and topographical prerequisites of the conventional pumped hydro energy storage, the use of underground cavities as water reservoirs allows countries without steep topography, such as Belgium, to increase the potential of the energy storage capacity. Belgium abounds in disused mines and quarries convertible into water basins. In this article, two Belgian case studies are presented and discussed for their singularity. A slate quarry in Martelange is discussed in technical aspects proposing three operating scenarios. Moreover, a preliminary economic analysis of the underground pumped storage system and a greenhouse gas emission evaluation for the storage system's lifetime are presented. The analysis for a 100 MW power plant estimates a total initial investment of over 12 million euros and two million of CO 2 avoided over its lifetime. This article also proposes the use of the coal mine 500 m deep of Pérronnes-lez-Binche. The mine representation discussed here offers a high energy capacity, but the substantial head drop (from about 500 to 200 m) challenges the selection of the hydraulic turbomachinery. A 1D simulation computed in SIMSEN draws out the behaviour of the unusual hydraulic configuration of turbines in series. [ABSTRACT FROM AUTHOR]

In December 2018, wastewater was officially recognized by the European Union as a renewable source of energy, thus wastewater heat recovery can be included in efforts to reduce greenhouse gas emissions. Given the fact that wastewater treatment plants can generate enormous heat surpluses, this decision gives leeway to couple the wastewater infrastructure with the energy system in order to increase energy efficiency at the system level, allow for power to heat solutions in order to integrate volatile renewable electricity generation and, thus, foster a sustainable energy transition and cleaner production. Yet, the success of these system integrations depends on the availability of energy consumers in proximity of the wastewater treatment plants, and the temporal patterns of energy supply and energy demand. So far, the importance of both temporal and spatial variations in performance of wastewater heat recovery systems have been discussed in literature, but only as separate considerations to date. In order to exhaust the potential of wastewater energy, the combination of both aspects still has to be studied sufficiently, and this paper aims at filling that gap. A three-step methodology is proposed, including an energetic analysis at the wastewater treatment plant, a spatio-temporal analysis of supply and demand in potential supply areas, and an integrated analysis, overlaying the supply and demand profiles. This allows to account for both the proximity of consumers and potential temporal mismatches between supply and demand. The methodology was applied on a case study in Ireland, being able to clearly identify potentials and pitfalls for laying out grids and dimensioning the energy generation systems. It can be concluded, that wastewater energy is a well-suited source of energy to supply baseloads, but the spatio-temporal patterns reveal that both periods of excess wastewater heat potentials as well as additional heating in bivalent systems is required. Therefore, the spatial – urban and regional – fabric, the mix of land uses and their density, largely determine the layout and the useable amount of this renewable energy source. Finally, it can be concluded, that the use of wastewater energy provides feasible and valuable contributions for sustainable urban energy supply systems and cleaner production if the electricity sources for the respective heat pump systems are renewable guaranteeing low-to zero-emission operation. Image 10 • An integrated spatio-temporal analysis of wastewater heat recovery is proposed. • 5 zones, within 2 km of the plant, were considered as a heat consumer. • On 21–136 days, the heat supply was insufficient to meet demand. • 58 % to 93 % of all demand can be supplied by the heat recovery system. • The recovered heat did not reach its full potential, due to temporal mismatches. [ABSTRACT FROM AUTHOR]