Simulation of the heat recovery use of R744 systems in a supermarket

This paper describes the outcomes a research project that investigate the improvement in the COP of an enhanced booster R744 refrigeration system that provided MT cooling for chilled food cabinets and LT cooling for cold room/frozen food cabinets by recovering the heat rejected and using it more for other building services applications in the supermarket. For instance, the heat reclaimed can be used for heating, HWS or to drive absorption chillers, either in whole or in part. To demonstrate the potential of the heat reclaimed within the supermarket and its impact on the store’s CO2e emissions, a feasibility study has been performed to examine the innovative system compared to of the existing conventional system which will cover the cooling demands of an existing supermarket. In order to achieve this, the data collected by a smart energy monitoring system will be used to examine the working of the novel system when covering the cooling demands of the store. The energy consumption of the novel system will be analyzed according to thermodynamic theory. Using an Excel model, the potential heat reclaimed will be mathematically investigated for best practice applications of heat recovery. The energy saved and CO2e emission reduction achieved in apply the novel system will be determined and analysed

Reflective Glass Effect on Energy Consumption and Food Quality in Delicatessen Cabinets

Retail supermarkets are responsible for around 3% of total electrical energy consumed in the United Kingdom and the most energy is used in refrigeration systems, particularly for operation of open displays such as delicatessen cabinets which consume approximately 50%. Although the cabinets are energy intensive, they are commonly used in supermarkets for displaying unwrapped chilled food stuffs. These cabinets are associated with the weight loss and quality deterioration of food stuffs being reported frequently as the cause for their high operational costs. This paper presents an investigation on the cause and rectification of weight loss in delicatessen cabinets. Specifically, the paper describes the effective use of low emissivity glass in reducing the impact of the thermal infrared radiation on the food temperatures and energy consumption

Performance Enhancement of Urban Ground Source Heat Pumps through Interactions with Underground Railway Tunnels

Ground source heat pumps (GSHPs) can provide an efficient way of heating and cooling buildings due to their high operating efficiencies. The implementation of these systems in urban environments could have further benefits. In such locations the ground source heat is potentially more accessible via alternative sources such as through underground railways (URs). This paper investigates to what extent the heat in the soil surrounding an UR tunnel could enhance the operation of urban GSHPs installations. To address this, a numerical investigation was set out which included a parametric study considering a number of geometrical options of the systems. The results showed that heat extraction rates of GSHPs installed near UR tunnels can be significantly improved by up to ~ 43%

A Na+ conducting hydrogel for protection of organic electrochemical transistors.

Organic electrochemical transistors (OECTs) are being intensively developed for applications in electronics and biological interfacing. These devices rely on ions injected in a polymer film from an aqueous liquid electrolyte for their operation. However, the development of solid or semi-solid electrolytes are needed for future integration of OECTs into flexible, printed or conformable bioelectronic devices. Here, we present a new polyethylene glycol hydrogel with high Na+ conductivity which is particularly suitable for OECTs. This novel hydrogel was synthesized using cost-effective photopolymerization of poly(ethylene glycol)-dimethacrylate and sodium acrylate. Due to the high water content (83% w/w) and the presence of free Na+, the hydrogel showed high ionic conductivity values at room temperature (10-2 S cm-1) as characterized by electrochemical impedance spectroscopy. OECTs made using this hydrogel as a source of ions showed performance that was equivalent to that of OECTs employing a liquid electrolyte. They also showed improved stability, with only a 3% drop in current after 6 h of operation. This hydrogel paves the way for the replacement of liquid electrolytes in high performance OECTs bringing about advantages in terms of device integration and protection

Sodium and Potassium Ion Selective Conjugated Polymers for Optical Ion Detection in Solution and Solid State

EPSRC. Grant Number: EP/G037515/1; EC FP7 Project SC2. Grant Number: 610115; EC FP7 Project ArtESun. Grant Number: 604397; EC FP7 POLYMED. Grant Number: 61253

Ionic Hydrogel for Accelerated Dopamine Delivery via Retrodialysis.

Local drug delivery directly to the source of a given pathology using retrodialysis is a promising approach to treating otherwise untreatable diseases. As the primary material component in retrodialysis, the semipermeable membrane represents a critical point for innovation. This work presents a new ionic hydrogel based on polyethylene glycol and acrylate with dopamine counterions. The ionic hydrogel membrane is shown to be a promising material for controlled diffusive delivery of dopamine. The ionic nature of the membrane accelerates uptake of cationic species compared to a nonionic membrane of otherwise similar composition. It is demonstrated that the increased uptake of cations can be exploited to confer an accelerated transport of cationic species between reservoirs as is desired in retrodialysis applications. This effect is shown to enable nearly 10-fold increases in drug delivery rates from low concentration solutions. The processability of the membrane is found to allow for integration with microfabricated devices which will in turn accelerate adaptation into both existing and emerging device modalities. It is anticipated that a similar materials design approach may be broadly applied to a variety of cationic and anionic compounds for drug delivery applications ranging from neurological disorders to cancer

Controlling the mode of operation of organic transistors through side-chain engineering

Electrolyte-gated organic transistors offer low bias operation facilitated by direct contact of the transistor channel with an electrolyte. Their operation mode is generally defined by the dimensionality of charge transport, where a field-effect transistor allows for electrostatic charge accumulation at the electrolyte/semiconductor interface, whereas an organic electrochemical transistor (OECT) facilitates penetration of ions into the bulk of the channel, considered a slow process, leading to volumetric doping and electronic transport. Conducting polymer OECTs allow for fast switching and high currents through incorporation of excess, hygroscopic ionic phases, but operate in depletion mode. Here, we show that the use of glycolated side chains on a thiophene backbone can result in accumulation mode OECTs with high currents, transconductance, and sharp subthreshold switching, while maintaining fast switching speeds. Compared with alkylated analogs of the same backbone, the triethylene glycol side chains shift the mode of operation of aqueous electrolyte-gated transistors from interfacial to bulk doping/transport and show complete and reversible electrochromism and high volumetric capacitance at low operating biases. We propose that the glycol side chains facilitate hydration and ion penetration, without compromising electronic mobility, and suggest that this synthetic approach can be used to guide the design of organic mixed conductors

Molecular Design of Semiconducting Polymers for High-Performance Organic Electrochemical Transistors.

The organic electrochemical transistor (OECT), capable of transducing small ionic fluxes into electronic signals in an aqueous environment, is an ideal device to utilize in bioelectronic applications. Currently, most OECTs are fabricated with commercially available conducting poly(3,4-ethylenedioxythiophene) (PEDOT)-based suspensions and are therefore operated in depletion mode. Here, we present a series of semiconducting polymers designed to elucidate important structure-property guidelines required for accumulation mode OECT operation. We discuss key aspects relating to OECT performance such as ion and hole transport, electrochromic properties, operational voltage, and stability. The demonstration of our molecular design strategy is the fabrication of accumulation mode OECTs that clearly outperform state-of-the-art PEDOT-based devices, and show stability under aqueous operation without the need for formulation additives and cross-linkers

N-type organic electrochemical transistors with stability in water.

Organic electrochemical transistors (OECTs) are receiving significant attention due to their ability to efficiently transduce biological signals. A major limitation of this technology is that only p-type materials have been reported, which precludes the development of complementary circuits, and limits sensor technologies. Here, we report the first ever n-type OECT, with relatively balanced ambipolar charge transport characteristics based on a polymer that supports both hole and electron transport along its backbone when doped through an aqueous electrolyte and in the presence of oxygen. This new semiconducting polymer is designed specifically to facilitate ion transport and promote electrochemical doping. Stability measurements in water show no degradation when tested for 2 h under continuous cycling. This demonstration opens the possibility to develop complementary circuits based on OECTs and to improve the sophistication of bioelectronic devices