E41: Solar Hot Water Collectors – Above Green

Requirement Summary

This measure can be claimed if solar water heating is specified.

Intention

The installation of solar water heating will reduce the grid electricity (fossil fuels) used by the building for water heating.

Approach/Methodologies

To recognize energy reductions from installing solar collectors, a user must enter the proportion of hot water demand in the improved case that the solar collectors will deliver. EDGE uses this percentage to offset the amount of energy needed, displaying an approximate minimum area of collectors required to deliver the proportion of hot water demand. This will help auditors to check the size of the solar system against the EDGE estimate.

The amount of hot water delivered by the solar collectors is dependent on the amount of solar energy available, the roof pitch and profile, space available, shading factors, the orientation and angle of the solar collectors, and the type of solar collectors. The size of the storage tank also impacts the amount of hot water delivered, as a tank that is too small will reduce the quantity that can be stored. These factors should be considered by the design team.

Solar collector sizing calculators are available from manufacturers of solar collectors. Alternatively, online calculators or software can be used.

In some cases, solar collectors are centralized for a combination of buildings within the building project. In these cases, the central solar plant should be located within the site boundary of the project, or managed by a company within the control of the site owner. This is to ensure continued and sustainable management and access to the plant for future maintenance.

When solar hot water collectors are located off-site, then a contract with the management company in charge of the PV system must be provided as part of the documentation at post-construction stage.

Potential Technologies/Strategies

The two types of solar thermal collectors are flat plate and evacuated tube. Both types of solar collectors should ideally be installed at a tilt angle that takes advantage of the most useful altitude angles of the sun to maximize the solar heat available. This angle is approximately equal to the building location’s latitude. The collectors should be angled towards the equator (towards the south in the northern hemisphere, and towards the north in the southern hemisphere). If this is not possible then facing the panels towards the southeast, southwest or even west is also acceptable, but panels should not be installed to face north in the northern hemisphere, and towards the south or east in the southern hemisphere. Solar collectors can also be installed horizontal to the ground. This is optimal in locations where the sun’s azimuth (angle of the sun from the horizon) is vertically overhead at the desired peak production times. Where the sun is at other angles, the efficiency is adversely affected.

Table 52: Types of solar water collectors

Type	Description
Flat Plate Collectors	As their name suggests, they are flat and typically black. They are the most commonly used collectors and are the cheapest option. Flat plate collectors consist of an absorber plate, which is usually black chrome; a transparent cover which protects the absorber plate and reduces heat loss; tubes containing a fluid to take heat from the absorber plate; and an insulated backing.
Evacuated Tube Collectors	Evacuated tubes consist of a row of glass tubes. These glass tubes each contain an absorber plate fused to a heat pipe containing heat transfer fluid.

Relationship to Other Measures

This measure is inextricably linked to hot water consumption, which EDGE estimates based on the number of occupants, the efficiency of the hot water boiler, and the flow rates of the kitchen, showers, laundry and hand basin faucets. The required area of solar thermal collectors can therefore be reduced significantly by specifying low-water-use showers and faucets, as well as any water heating recovery technology.

Assumptions

The base case assumes that no solar thermal collectors are installed. The default improved case assumes 50% of total hot water demand in the improved case being met by the solar thermal installation. The default value of 50% must be overwritten by the user with the actual percentage applicable to the project. The area of the collector required to deliver the stated proportion of hot water demand assumes that flat plate collectors are used, and assumes that the collectors are installed at an optimum angle.

Compliance Guidance

To demonstrate compliance, the design team must briefly describe the system including the type of solar collector; the capacity of the storage tank and its location; and the size, orientation and installed angle of the panels.

EDGE will display the approximate area of panels required to deliver the proportion of hot water claimed by the design team. The required area is calculated using local climate data and assumes an optimum angle for the solar panel installation. The calculations assume use of flat plate collectors, therefore if the design team is using evacuated tube collectors the area can be reduced.

Design Stage

Post-Construction Stage

At the design stage, the following must be used to demonstrate compliance:

Roof plan and drawings showing location, orientation, and angle of the panels, which must be at least as much as the area estimated by EDGE; and
Manufacturer’s data sheet for the panels specified; or
Building’s hot water system schematic including solar panels.

At the post-construction stage, the following must be used to demonstrate compliance:

As-built plumbing schematics; and
As-built roof plan showing the location, orientation and angle of the panels; and
Photographs of the installed panels; or
Purchase receipts and delivery notes for the solar panels.