In this paper, a panel with a surface designed for radiative sky cooling is used to demonstrate the passive cooling of water below the dry-bulb temperature with no evaporative water losses, where the only energy input is to pump water. For a surface area of 0.74 m² (8 ft²), we demonstrate water cooling of 3°C (5.4°F) below the dry-bulb temperature at a water flow-rate between 6-9 L/hr (1.6-2.4 gal/hr). This corresponds to an effective heat rejection rate between 40 and 100 W/m² (13 and 32 Btu/hr-ft²).

One possible application of these panels is to serve as a modular cooling tower, replacing a traditional cooling tower in a water chiller system. This might be desired under conditions when water resources are constrained, and high efficiency cooling is required. To demonstrate the benefit of the cooling panels on a water chiller system, a thermodynamic analysis using the TMY3 dataset (typical meteorological data) from Las Vegas, NV is presented and the benefit on a typical office building’s cooling system is assessed.

In the present simulation study, the coupling of nighttime radiative cooling with PCM for cooling an office room was investigated. For cooling water through nighttime radiative cooling two types of solar panels were utilized, an unglazed solar collector and photovoltaic/thermal (PV/T) panels. Apart from cold water for space cooling, the installation was capable of providing domestic hot water from both types of panels and electricity from the PV/Ts. This system was simulated for the period from 1^st of May until 30^th of September, under the weather conditions of Copenhagen (Denmark), Milan (Italy) and Athens (Greece).

In Athens and Milan the operative temperature was within the range of Category III of EN 15251 (23 – 26^oC, 73.4 – 78.8^oF) for 81% and 83% of the occupancy period respectively, while in Copenhagen it was within the range only for 63%. Furthermore, the percentage of PCM used at the end of the occupancy period was 86%, 81% and 80% for Copenhagen, Milan and Athens, respectively. Nighttime radiative cooling provided for Copenhagen 61%, for Milan 36% and for Athens 14% of the cooling energy required for discharging the PCM. Furthermore, the average cooling power per unit area provided by the PV/T panels was 43 W/m² for Copenhagen, while for Milan and Athens it was 36 W/m² and 34 W/m², respectively. The cooling power of the unglazed solar collector was negligible. Finally, the total electricity produced in Copenhagen for the simulated period was 371 kWh, while for Milan and Athens it was 380 and 439 kWh, respectively.

It was concluded that the nighttime radiative cooling can be a satisfying solution for providing space cooling to office buildings. The performance of the installation could be improved by implementing a solar shading system and a more precise control strategy.

Commercial hot water heating in the US accounts for 780 Trillion Btu/year of primary energy use, with over half of this amount from natural gas fired heaters. A commercial absorption heat pump could achieve a level of savings much higher than possible by conversion to the best available non-heat-pump gas fired alternatives (instantaneous condensing). The ammonia-water system has the added advantage of zero Global Warming Potential and Ozone Depletion Potential. This seminar presents the development of a practical absorption heat pump cycle with laboratory-measured performance metrics, outlines potential installation layouts, and presents the economic case for adoption in commercial buildings.

Utilizing low grade thermal energy and hot water for cooling is a great application for Double and Triple Lift absorbers.  This presentation will cover a new Tire Plant in Tennessee that will use 185-131 F hot water to produce 300 tons of cooling.  Currently there is a dearth of general understanding of what a double or triple lift unit is and therefore not many applications to date in North America.  Traditional and well know single stage absorber cannot use hot water below 190F typically.

Recently fuel cell based mCHP systems have been proposed as a means of providing both heat and power for the residential sector. These systems are meant for power generation at high efficiency and low emissions, but the heat can still be recovered for space or hot water heating. These systems are still under development and significant research is being conducted to determine if fuel cell based systems can match the load requirements of a typical household. Despite the work performed, different studies have had drastically different conclusions for the fate of fuel cell systems leaving many unanswered questions for the future.

A systematic review of current literature was undertaken to assess fuel cell based mCHP for the residential sector. The review highlighted many of the technical challenges facing these systems while also uncovering significant benefits and opportunities. In this paper, the results of the review are presented and an analysis of current trends and future priorities assessed. Fuel cell based mCHP is shown to have significant potential in reducing emissions and conserving natural resources while maintaining current building performance.

The TSO model enables a new approach for the selection and operation of CHP units that encompasses whole life costing, carbon emissions as well as half-hourly energy prices and demands throughout the day, seasonally and annually, providing a more comprehensive result than current methods. Utilising historic metered energy demands, projected energy prices and a portfolio of available CHP technologies, the mathematical model solves simultaneously for an optimal CHP unit selection and operational schedule for a determined building based on a preferred objective. The objective can either be: minimum cost, minimum GHG emissions, or a mix of both for an operational period that satisfies the store's energy demands. The model defines which unit to acquire and its power output for each half-hourly interval for different day types and a given time period.

The TSO model was implemented for a sample of 35 buildings from a group of over 1300 stores that belong to a supermarket chain in the UK. These varied in characteristics such as heat-to-power ratio, size, and electricity pricing region. It was identified that the majority of stores assessed could reduce their operational emissions more than 70% while providing returns on investment above 100% by installing low-carbon co-generation units. Results of this model prove that attractive cost and emissions savings are possible through the optimal selection and operation of CHP technologies fuelled by bio-methane.

For gas HPWHs, it is found that using typical component efficiencies, EF will be 75-90% of the heat pump cycle COP. The contribution of each parameter to the difference between EF and cycle thermal COP is as follows: burner efficiency accounts for 50-80% of difference, parasitic electrical draws for 10 – 30%. Independent of COP, the presence of a condensing heat exchanger can make a 5-10% difference in EF, and tank losses reduce EF by 6 – 10%, depending on the insulation level.

In this work, the response of a tank that is stratified during heating is compared with the response of a tank that is mixed during heating, for first hour rating (FHR) and energy factor (EF) testing. Experimental results from FHR, EF, and UEF tests on a CO2-based HPWH with wrap-around coil and stratified tank are used to validate a simulation model. The implications on FHR, EF, and UEF of tank stratification are analyzed and discussed.

In order to study the energy and exergy performances of air-based and water-based systems, an air heating and cooling system, and a radiant floor heating and cooling system were chosen, respectively. A single-family house was used as a case study assuming that different space heating and cooling systems were used to condition the indoor space of this house. In addition to the thermal energy and exergy inputs to the system, energy and exergy inputs to the auxiliary components were also studied. Both heating and cooling cases were considered and three climatic zones were studied; Copenhagen (Denmark), Yokohama (Japan), and Ankara (Turkey).

The analysis showed that the water-based radiant heating and cooling system performed better than the air-based system both in terms of energy and exergy input to the heating/cooling plant. The relative benefits of the water-based system over the air-based system vary depending on the climatic zone. The air-based system also requires higher auxilliary energy input compared to the water-based system and this difference is mainly due to the required air-flow rates to address the heating and cooling demands, indicating a clear benefit for the water-based system over the air-based system.

The auxilliary energy and exergy input to different systems is an important parameter for the whole system performance and its effects become more pronounced and can be studied better in terms of exergy than energy. In order to fully benefit from the water-based systems, the auxiliary energy use should be minimized.

One of the larger sets of external information for a project is the HVAC cooling and heating loads. By exporting space properties (i.e. Name, No., Floor Area, etc.) from Revit thru gbXML to load & energy analysis software, data entry time and errors are reduced.  Once HVAC loads are completed the calculated results can be brought back into the Revit model. This allows a Space Airflow Schedule in Revit to be utilized by engineers to also show diffuser airflows.  Calculated airflows are calculated from the Load software. This removes the need to go to each view/sheet and edit and sum airflows. Once diffusers have airflows, then the ductwork sizes can be reviewed and adjusted by using velocity and pressure drop diagrams in Revit. These color coded ductwork diagrams can be setup to flag or highlight a section of duct that falls out of a company’s design standard tolerance range. The airflow from all the diffusers that connects to a piece of equipment is also able to be verified and checked in a Schedule against the scheduled airflow value. The gas load in a schedule for any piece of equipment can also be used to drive gas flow (CFH) thru the gas piping systems.  This process is dynamic which saves the time of adding up CFH values. Revit also provides the ability to perform ASHRAE 62.1-2007 ventilation calculations for constant volume single zone systems.  The setup is very easy at the beginning of a project and also dynamically updates if the design changes.

The calculations and design workflows outlined above are just the beginning of the potential productivity gains.  Other gains come from Fixture Unit propagation for Sanitary and Vent systems, and even the area served by roof drains.  These productivity gains require some investment time to set up workflows, schedules and views.  This investment will not only provide additional productivity and consistency, but also better quality control resulting from all of the information residing in one location.