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.

Energy retrofits for commercial buildings focus on installing high-efficiency boilers, motors, and lighting.  However, efficiency gains from equipment can be offset by occupant discomfort due to inefficient windows, which can account for 25 percent of a typical building’s heating load in cold climates and 50 percent of the cooling load in warm climates, according to the U.S. Environmental Protection Agency.  Because equipment is sized to service a specific building’s needs, improving a building’s envelope should be addressed first, so that smaller equipment can be specified, saving on the upfront and ongoing costs.

A variety of options exist for improving the energy performance of existing commercial glazing systems including: Application of interior window films – solar heat gain. Complete window rip-out and replacement – solar heat gain and improved U-factor. Interior commercial storm windows - improved U-factor. Interior installed Low-E retrofit insulating glass unit - solar heat gain and improved U-factor

Each alternative has specific performance benefits and associated cost and convenience implications.  Solar heat gain is a primary problem with most commercial buildings having lower performance, single-glazing, regardless of climate zone.  This leads to increased cooling loads, larger sizing of HVAC equipment, higher energy costs and lower occupancy comfort levels.  Any improvement in the glazing system should incorporate technology to reduce the impact of solar heat gain through the use of high performance low-e coatings.  Concurrently for heating dominant climate zones, a substantial reduction in U-factor acts in parallel to reduce HVAC demand for heating, reduces energy costs and improve occupancy comfort levels.

This paper compares the performance benefits, cost implications and occupancy comfort factors for each of these systems with a focus on the advantages of an interior installed low-e retrofit insulating glass unit.  Such a system has been demonstrated to provide the full benefits of a rip-out and replacement at approximately 40% of the installed cost.  It includes independent case study energy analysis, installation and cost comparison, testimonial on occupancy comfort and sustainability attributes.

To investigate the impact of  environmental control on occupants’ comfort, satisfaction level and subjective productivity, four identical side-by-side offices with different control setups and interfaces, ranging from fully automated to fully manual and from low-level of accessibility (wall switches) to high-level of accessibility (remote controllers or modular web interfaces) were selected for the purpose of this study. The experimental study includes monitoring of physical variables, actuation and operating status of building systems and online surveys of occupants’ perception of environmental variables as well as their personal characteristics and attributes.

Compared to previous studies conducted in buildings with non-motorized blinds and artificial lights without dimming options, our results show substantial differences in dynamics and frequency of human-shading and –electric lighting interactions for buildings equipped with this advanced technology. Moreover, it was found that comfort with amount of light and visual conditions, satisfaction with window view, and subjective productivity are all maximized in offices with manual control setups and occupants are comfortable with a wide range of indoor illuminance when they have control over their environment. These results also demonstrate occupants’ strong preference for customized indoor climate and the outcomes support the development of personalized controls, which will be discussed in the paper.

 In a major Japanese laboratory animal facility, a multiplexed IAQ sensing system which continually measures certain types of IAQ values at multiple locations was installed, and VAV control which varies ventilation rates based on those IAQ measurements was implemented. Because it was a first trial of automated DCV in Japan, target areas were confined to two (one rodents’ and one primates’) animal holding rooms, and a step-by-step approach was taken as follows. 1) In order to find out the correlation between ventilation rates and IAQ values, ventilation rates was changed manually (6, 9, 12, 15 ACH for every 2 weeks) with continuing multiplexed IAQ sensing. 2) Based on the results of the foregoing analysis, automated DCV in accordance with concentration differences between supply and room (or room exhaust) air was implemented. The DCV was tried under the conditions of three series of set points (“low”, “middle” and “high”). In the case of “low” set points, ACH varied synchronized with animal biorhythm (circadian rhythm) and total ventilation was saved by 20.6-27.5%. On the other hand, in the case of “high” set points, ACH almost did NOT increase except during the in-room activity (e.g., cage changing or room cleaning) and total ventilation was saved by 47.5-48.7%

This paper will present the details of the mechanical ventilation and cooling design for a science facility located 4,850 ft underground in a former gold mine. The site will be comprised of 3 large caverns and a network of tunnels to be excavated over 6 phases. The installation of airside and waterside equipment will take place as the excavation proceeds posing operational challenges in meeting the space requirements. Mine ventilation air will be cooled and supplied to the experiment caverns through water cooled air handling units picking up heat from the spaces. Exhaust fans remove air from the space meeting the air change requirement and deliver the air to an underground spray chamber. The spray chamber is an excavated space where condenser water from the chiller is sprayed into the exhaust airstream. The exhaust airstream picks up heat from the sprayed water and returns to the surface through a vertical borehole while cooled condenser water returns to the chillers.

The paper also presents the constructability considerations which are a result of the phased excavation and operation of the facility. The mechanical design is flexible to limit the incremental changes between phases while maximizing the use of the excavated space and minimizing the client’s costs.

As the HVAC&R industry is subject to greater performance efficiency requirements, measurement accuracy for airflow becomes a critical issue.  The accuracy of many instruments for the measurement of temperature, pressure, humidity, and power has improved over the past couple decades.  New test standards now require the evaluation of the uncertainty of measurements and derived values.  These developments have raised questions about what can be realistically expected for the accuracy of the multi-nozzle chamber air flow meter (AFM), especially due to the lack of open literature test data with multi-nozzle configurations.

To determine the accuracy (or uncertainty) to be expected from typical multi-nozzle chambers, a four-nozzle AFM was constructed in strict accordance with current standards and tested at an independent, multi-industry, gas flow test laboratory.  The test laboratory used their primary National Institute of Standards and Technology (NIST) traceable critical flow Venturi test method with an average uncertainty of +0.3% of the flow.  Six nozzle flow configurations consisting of each of the four nozzles separately, a particular combination of three nozzles and all four nozzles simultaneously, were each subjected to three nozzle throat velocities for a total of 18 different tests.  The velocities included the lowest and highest defined by industry standards and one intermediate velocity.

The test laboratory utilized their NIST traceable, independent mass flow measurement in series with the test AFM and included a measurement of three required parameters: nozzle differential pressure, inlet temperature, and barometric pressure.  Dry air was used to eliminate errors associated with the calculation of moist air properties.  Confirming air mass flow rates were calculated using the nozzle diameters, nozzle flow coefficients, and the measured parameters.  The results of all 18 flow rate tests were compared and shown to be within +0.2 to +0.4%.  This project demonstrates that a typical multi-nozzle AFM, when constructed in accordance with industry standards, can be used for air flow measurements that are accurate to better than +0.4% of reading over the entire flow range.

Results from the linear correlation development show that ECM blower efficacies can be accurately predicted by using blower rotational speeds as evidenced by the high R² values ranging from 0.961 to 0.981. For the six tested ECM blowers, the linear factor for the developed correlations varies from -2.881 to -2.657, and the offset factor is in a range of 3.287 to 3.551. Furthermore, a comparison between the predicted and measured efficacies shows an accuracy of ±15% for the developed correlations.

Results generated from this study provide a method to predict the energy performance in terms of efficacies for ECM blowers based on the knowledge of rotational speed. In addition, the experimental data and correlations produced in this study can be used to model the ECM blower efficacy behaviors at different operating speeds.

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.

This paper compares minimum ventilation requirements for operating rooms and procedure rooms, from four international standards. The standards compared are; ASHRAE-170 Ventilation for health care facilities (US),  DIN-1946 – VAC systems in buildings and rooms used in the health care sector (Germany), HTM-03-01 Specialized ventilation for health care premises (UK), and UNE 100713 Instalaciones de acondicionamiento de aire en hospitales (Spain).

The comparison identifies the minimum (i.e. most permissive) ventilation requirements in six different requirement areas:  outdoor air ventilation, total room air ventilation, supply air filter efficiency, room temperature, room humidity and room pressurization.  Results are normalized to common units, compared and discussed in context of the four standards.

This paper compares minimum ventilation requirements for operating rooms and procedure rooms, from four international standards. The standards compared are; ASHRAE-170 Ventilation for health care facilities (US),  DIN-1946 – VAC systems in buildings and rooms used in the health care sector (Germany), HTM-03-01 Specialized ventilation for health care premises (UK), and UNE 100713 Instalaciones de acondicionamiento de aire en hospitales (Spain).

The comparison identifies the minimum (i.e. most permissive) ventilation requirements in six different requirement areas:  outdoor air ventilation, total room air ventilation, supply air filter efficiency, room temperature, room humidity and room pressurization.  Results are normalized to common units, compared and discussed in context of the four standards.

This paper outlines three alternatives for addressing ventilation in outpatient facilities, within and out of the context of the current ASHRAE Standard 170 “Ventilation for Health Care Facilities”. It compares the current requirements of Standard 170 to those of B occupancy areas in outpatient health care facilities such as medical office buildings (MOBs) and ambulatory surgery centers (ASCs).

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.

Measurements of performance at the AHRI Standard 210/240 rating points were made with each refrigerant.  In addition, tests were run under outdoor temperatures ranging from 65F to 125F (18C to 52C).  A simple thermodynamic cycle model that matches average saturation temperatures in the evaporator and condenser along with a common compressor isentropic efficiency indicates that the capacity with DR-55 should be 2.5% lower than with R410A and should have an efficiency 1% higher.  Actual performance with DR-55 matched the capacity of R410A at the same compressor speed (60 Hz) with an efficiency 4% higher.  Similarly positive results were obtained with DR-5A.  With R32, the compressor speed needed to be reduced to 53 Hz to match the baseline capacity.  Efficiency was 3% higher than baseline.  As expected, R32 produced compressor discharge temperatures (CDTs) that were elevated by 20F and increased to 40F at the higher ambient conditions over R410A while DR-55 and DR-5A CDTs were only 10F above the baseline.  

The results here demonstrate that DR-55 and DR-5A are "design compatible" alternatives to R410A.  That is, they can be used in existing equipment designs with very little modification.

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.