Page 97 - Hong Kong Green School Guide

3. Green School Guide - 3.3 Energy Saving
Hong Kong Green Building Council 95
Benefits
• Utilise ‘free’ resource in the form of solar energy to heat water;
• Reduce carbon emissions generated through heating water by other means;
• Practical feature that can provide hands-on-learning experience for students
to learn about renewable energy; and
• 800 kWh/m2 (of solar panel area) of electricity can be saved per year through
solar heating of water. This is enough to operate a 25-Watt light bulb for three
and a half years.
Issues to Consider
a. Opportunities
• Solar hot water systems can be installed on the roofs.
b. Constraints
• Shading from surrounding buildings, hence insufficient sun light;
• Structural loading to the roof due to additional weight and wind effect;
• Compliance with The Provision of Means of Escape in Case of Fire, roof
designated as refuge floor should not be obstructed by the installation;
• Water proofing & potential water seepage issue during installation;
• Plumbing issues, e.g. water supply point, insufficient water pressure to roof;
and
• Electrical issues, e.g. electrical supply at roof for heating elements and
controls.
c. Solutions
• Select roof area with sufficient daylight;
• Two collector types for solar hot water system: Flat-plate collector and
evacuated tube collector. Generally, evacuated tube collectors are more
efficient than flat-plate collector because they require a smaller installation
for the same output, but they are more expensive;
• Ideal solar collector orientation is tilted at 22 degrees latitude angle to the
south facing;
• Authorised Person (AP) and Registered Structural Engineer (RSE) shall
be consulted for aspects related to the structural loading capacity of roof,
alterations and additional works to the existing building structure to support
3.3.10 Solar Hot Water System Applies to NS & ES