CONSTRUCTION IN A DEMANDING CLIMATE


the floor. Air moves through the breeze wall and through the rocks to the plenum on the opposite side, picking up heat from the rocks or losing heat to them, depending on the relative temperatures. When desired, this tempered air is fed into the fan-driven ventilation system that supplies air to the clinical spaces, and which then cascades through transfer grilles to the sub-waiting areas. This system is augmented by individually controlled split air conditioning units in the clinical spaces to bring the temperature to the desired level. The combination of chimneys and rock stores thus forms a passive system to reduce the energy consumption of the split air-conditioning units, by pre-heating or pre-cooling the fresh intake air before it is distributed into the facility.


Preliminary results (August 2018) Capital expenditure: The total project construction cost was ZAR 19.3 m, which is considerably less than the cost of a similar-sized clinic with conventional HVAC which was completed at the same time. It must be noted that the winning bidder had priced very competitively at the time.


Energy performance: Not much data is available for clinics generally, as systematic monitoring was only commenced recently. The Riversdale, Wellington, and Grassy Park Clinics in the Western Cape were used in this study to calculate the energy consumption of an “average clinic”.


The initial results for Hillside were very disappointing. During September and October the energy usage per square metre was 30% and 20.5% above that of an average clinic. Following an investigation, several items were found to have been incorrectly installed. Most notably, some of the fans were operating in reverse. After corrective actions were implemented, the energy performance of the clinic improved markedly. When the monthly kWh usage per square metre for the Hillside Clinic over a six-month period is compared to the average usage of a similar clinic, the Hillside Clinic performs significantly better during autumn, and uses 40% less energy usage than similar facilities. Further investigation revealed that the relatively poor winter performance is due to the incorrect programming of some of the rock store controllers, which continue operating in summer mode, thereby supplying the clinic with colder air via the rock stores. This programming error is being remedied.


According to the South African National Standard for Energy Efficiency in Buildings (SANS 204-1), the peak energy demand and consumption for a G1 classification of use (consulting rooms or offices) in the climatic zone 2


32 Health Estate Journal May 2020


10 9 8 7 6 5 4 3 2 1


0 March April May Month Monthly energy consumption of Hillside Clinic vs. ‘Average Clinic’.


(Temperate Interior) is 75 VA/m2 190 kWh/m2


and /annum respectively.


Hillside Clinic had a peak energy demand of 37.5 VA/m2


, and an annual energy consumption of 73 kWh/m2 , or


approximately 50% and 62% below the maximum respective figures allowed by the standard.


Energy savings: The annualised average monthly energy consumption of the Hillside Clinic, compared with an “average clinic”, indicates an annual energy saving of ZAR 26,574.20 (2018). Indoor air quality: A comprehensive study of the performance of various features of the clinic was undertaken by the Council for Scientific and Industrial Research (CSIR), a recognised South African research institute. This study included an analysis of the indoor air quality (IAQ) and the indoor environmental quality (IEQ). Indoor air quality was assessed by using carbon dioxide (CO2


) levels as


to the outdoor levels provides an indication of the number of times the air has been re- breathed by the occupants of the clinic, and thus an indication of the risk of infection. Measured CO2


a proxy for the concentration of respiration-derived airborne pathogens such as TB. Comparing the indoor levels of CO2


levels indicate the outdoor reference level as 420 ppm,


which compares favourably to the main waiting area at 543 ppm, with 14 occupants at the time of measuring. When the waiting area was later re- measured with 31 occupants present, the reading increased to 614 ppm. The relatively small increase in CO2


levels


indicates that the ventilation system was providing an adequate volume of fresh air, especially considering that all windows and doors were closed during the measurement period. Indoor temperature: Although the results give a good indication that the central ventilation system is working, the temperature measurements show that the rock stores alone are not providing adequate warming or cooling of the air to an appropriate comfort level temperature of approximately 24˚C. Indoor thermal comfort is therefore adjusted using additional warming and cooling through split AC units in clinical spaces throughout the facility.


Lessons learned


Hillside Clinic has now been in use for approximately one year. Measuring and analysing data did not commence immediately, but early indications are that the facility design decisions are indeed having the desired benefits, and should be considered when designing new facilities.


Table 3. Annual electricity consumption of Hillside vs. ‘Average’ Clinic. Annual consumption


Annualised Energy (kWh/m2 Typical floor area (m)


Beaufort West kWh tariff (ZAR/kWh)


Service charge (ZAR) per annum


Total annual electricity costs Annual energy cost (ZAR)


Annual saving (ZAR) /Year) Total energy usage (kWh/Year)


Hillside Clinic 73


1045 76,360


0.84 2640


R 66,782.40 R 26,574.20


Average Clinic 104


1045 107,996


0.84 2640


R 93,356.64 June July August


9.1 8.7 8.1 7.1 6.7 6.3 5.6 5.1 5.8 6.0 8.2


9.3


n Hillside Clinic n Typical Clinic


Energy consumption (kWh/month/m2


)


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