CASE STUDIES OF THE PERFORMANCE OF PCM IN BUILDING ENVELOPES

PCM storage is likely to become a viable technology in the next few years. For instance, it can be concluded that PCM-based thermal storage in conjunction with an electric air-source heat pump, offered as part of a Green Deal, could be technically possible in retrofit buildings. Also, the introduction of a thermal store as part of a heating system offers a potential economic impact, through the requirements for initial installation and ongoing maintenance. Moreover, the use of latent heat energy storage is finding applications in the built environment with PCMs used in building cooling systems to displace peak cooling loads and by using microencapsulated PCMs in the building fabric. This paper also displays some case studies on the performance of PCMs in building envelope as follows.

COOL-PHASE Notre Dame School Building

Two COOL-PHASE systems with PCM were installed in an IT classroom (approximately 70 m2) where the system was required to overcome high internal heat gains through 30 PCs and glazing in April at Notre Dame School Building (London) [130]. Also, two control rooms (one room with similar internal heat gain and another one with much lower internal and external heating load) were chosen to provide a comparison to the performance of the COOL-PHASE systems. During the experiment, temperature and CO, levels were monitored every minute and collected by data logger during the spring term. Therefore, the results show that the average temperatures increased in the control room slightly between spring and summer term due to warmer weather (Figure 14.12).

Comparison of the temperature before and after the install. (From COOL- PHASE system in IT classroom, Available

FIGURE 14.12 Comparison of the temperature before and after the install. (From COOL- PHASE system in IT classroom, Available: http://monodraught.vertouk.com/documents/ downloads/download_34.pdf, May 17, 2011.)

However, the room with the COOL-PHASE system has seen a significant reduction in the average temperatures before and after the install. Therefore, it is clear that the COOL-PHASE system has had a significant impact on average temperatures as PCM with high-energy storage density stores energy over a limited range of temperature variations. Also, it would deliver financial savings of more than 26% (approximately £10,000) and C02 savings of 12.8 tons over the anticipated system lifespan of 20 years.

COOL-PHASE Owen Building at Sheffield Hallam University

COOL-PHASE was also installed in a particular “problem” room in the Owen Building at Sheffield Hallam University [131]. It is a 90-person teaching room on the tenth floor that consistently exhibited poor air quality and high temperatures. The room had no mechanical ventilation and was fitted with opening windows to one side; but due to the height of the building, these were restricted to a 100 mm maximum opening, limiting the effectiveness of natural ventilation. In November 2009, an initiated environmental check was taken by the university’s Estates Department to record the C02 levels change and temperature change. COOL-PHASE was installed in March 2012, and the performance was monitored throughout the late March warm spell and recorded a room temperature peak of 23°C when outside temperatures were hovering around 21°C. The results displayed that the temperatures were consistently recorded at 25°C at a time when November’s outside temperatures were reaching only 5°C. Moreover, the COOL-PHASE system was working harder to bring the C02 levels down during these peaks and, once the levels had been controlled, COOL-PHASE maintained CO, levels at around 600 ppm for the rest of the time. Therefore, the system has dramatically reduced CO, levels and is controlling previously excessive room temperatures well within normal comfort zones. All this w'hile reducing energy consumption by up to 90% compared to conventional mechanical cooling systems.

New Ford Retail Car Showroom

A new Ford retail car show'room and used car sales office completed in January 2013 is equipped with COOL-PHASE, a low-energy cooling, ventilation, and heat recovery system [132]. The result can be estimated that the system uses intelligently controlled PCM to actively ventilate and cool buildings, maintaining temperatures within the comfort zone, while radically reducing energy consumption by up to 90% compared to conventional cooling systems. Also, COOL-PHASE reduces the running costs of buildings while creating a fresh and healthy indoor environment without the use of compressors or hazardous coolants.

Sustainable Building Envelope Center

A composite flooring system that incorporates under-floor heating and PCM in the Sustainable Building Envelope Centre (SBEC) (Figure 14.13). A prefinished steel composite floor has been installed on the first-floor level of the building with PCM added to the concrete mixture just above the steel deck. In this application, PCM is being used to store, buffer, and release heat via the high emissivity prefinished

PCM in composite floor decking at SBEC, Tata Steel, Shotton works, UK

FIGURE 14.13 PCM in composite floor decking at SBEC, Tata Steel, Shotton works, UK. (From PCM in composite floor decking at SBEC, May 22, 2011.) steel floor deck that acts as a ceiling to the meeting room below. Excess heat load from usage is absorbed by the PCM and released when the heat load is reduced, providing a constant temperature. Therefore, the room temperature of the building can be controlled without heavy reliance on carbon-intensive fuels. The system allows cool or warm water to circulate through a network of water pipes embedded into the concrete to thermally activate the floor, providing highly effective cooling and heating method for the structure. It also can provide a constant and comfortable room temperature to be maintained during use, thereby reducing CO, emission.

Sir John Liang Building Coventry University

PCM technology with 1590 PCM TubelCE in total was installed within the Architecture Studio and two offices within the John Laing Building at Coventry University (Figure 14.14). The PCM Tubes are installed and respond to the surrounding temperature of the room. At the beginning of the day, the TubelCE are frozen, and as the room heats up due to body heat and heat from the sun, the PCM Tubes passively cool the room by absorbing the heat until completely melted. Over the night.

Schematic of PCM TubelCE installation in architecture studio in John Laing Building at Coventry University, UK

FIGURE 14.14 Schematic of PCM TubelCE installation in architecture studio in John Laing Building at Coventry University, UK. (From PCM TubelCE installation in Architecture studio in John Laing Building at Coventry University, UK Available: www.architect-bim.com/ resseepe-project-sustainable-innovations-installed-coventry-university/#.WSROqOsrKUk, May 22. 2016.)

TABLE 14.2

Comparison of Energy Consumption of Building with and Without PCM TubelCE

Boiler

Energy

(MWh)

Total

System

Energy

(MWh)

Total Nat. Gas (MWh)

Total

Carbon

Emissions

(KgC02)

Total

Energy

(MWh)

Total Energy (MWh/ m2

Previous energy consumption before PCM TubelCE installation

418.80

448.80

418.8

106064.00

448.80

0.12

Present energy consumption after PCM TubelCE installation

399.30

428.90

399.3

101614.00

428.90

0.11

Energy savings (%)

11.35

10.58

11.35

9.67

10.58

10.58

Source: PCM TubelCE Passive Cooling at Coventry University, UK, Available: www.pcmproducts.net/ files/John%20Laing%20Coventry-UK-%20Passive%20Cooling.pdf, May 23,2016.

as the temperature cools, so does the PCM. The PCM effectively loses energy to the immediate surroundings, charging for the next day.

In this project, the PCM technology provides free cooling with 230 kWh energy storage. The spaces and tubes will be energy monitored over the next year to gather full performance data, and the result shows that the new PCM system could save 10% total energy compared to the previous system (Table 14.2). Also, CO, emissions will be 48.15 kg/m2 per year, corresponding to more than 60% reduction. Associated investment costs to building renovation are expected to represent a maximum of 19% on average of the total costs of building an equivalent new building in the same location.

It can be concluded from the preceding case studies that PCM technology with passive cooling is increasingly being used in building envelopes because it has various benefits:

  • • Very low running cost;
  • • No external units are required;
  • • Highly energy-efficient system;
  • • Long life and a warranty for several years;
  • • Creates a healthy and productive environment for occupancy;
  • • High-performance ventilation and cooling system; and
  • • Environmentally friendly and sustainable solution that uses no refrigerants.
 
Source
< Prev   CONTENTS   Source   Next >