SunLizard Solar Air Heater/Cooler



    SunLizard Installation Notes & Photos
Performance Graphs


The SunLizard Solar Air Heater/Cooler was designed by Alternative Fuels & Energy, based in Mt Evelyn, Victoria.

Note: The design has changed slightly since I purchased mine. The Heating/Cooling flap (described below) is no longer at the bottom of the unit - It is now near the inlet & outlet vents, behind the PV Panel.

I wanted to try it out because my house has traditionally been quite cold in Winter. On a mild sunny Winter's day, the outside temperature can be a good several degrees warmer than in the main living area of the house. [See house description for background info on the house]. I'm hoping to make the Living Area a bit more pleasant to be in
Although a number of these units have been installed in Victoria and a few in other states, my system which was installed in November 2003, was the first in the Sydney area.

Sydney experiences a lot of cool but sunny days in Winter, which are ideal conditions for this type of unit. Whilst it may also provide useful heat on days with haze or high cloud, don't expect too much from the unit on rainy or heavily clouded days.

Theory of Operation:

The Sunlizard has primarily been designed as a heating unit. By rotating a flap at the bottom right hand corner of the unit, it can also be set for Venting / Cooling.

The 20 Watt Solar Photovotaic (PV) Panel mounted on the SunLizard is used to power the two fans inside the unit. The fans will only operate when there is sufficient sunlight reaching the panel.

Air flow when set for Heating
Winter / Heating Mode

The main unit which sits on the roof absorbs the infared rays from the sun, and heats the air within the unit. This works on a similar principle to a solar hot water system. When the flap is closed, the system becomes a 'closed circuit'.

By design, the fans will start working when the air inside the unit has started to warm up. Air from the room or area to be heated is drawn out through the ceiling vent and insulated ducting into the Sunlizard. The air is heated as it circulates through the unit. The warmed air then passes out of the unit, through some more insulated ducting and into the room/area to be heated through a wall mounted vent.

Air flow when set for Cooling / Venting.
Summer / Cooling / Venting Mode

When the flap is open, air from the room or area to be cooled is drawn through the ceiling vent and ducting into the Sunlizard's inlet vent. Rather than circulating through the Sunlizard, the air is vented outside. Cooler air can then flow into the house through floor vents or from gaps under doors.

Diagrams created by Hugh Todd

Main System Components:

Inlet & Outlet Vents in the loungerromThis is all that's readily visible of the system from the living area - The round Inlet vent in the ceiling, and rectangular wall outlet vent. The Laptop PC on the table is displaying and recording temperature data from the Datalogger.
  1. Sunlizard absorber box, mounted on the house/building roof
  2. Solar Photovoltaic (PV) panel which generates enough power to drive two fans within the Sunlizard.A ceiling mounted vent in the room/area to be heated
  3. A wall mounted vent in the room/area to be heated
  4. 150mm wide insulated ducting to connect the ceiling and wall vents to the Sunlizard
  5. (Optional) Datalogger and temperature sensors to monitor system performance.

There are a few other items required, which may vary with the site and installation method chosen.


I have a datalogger with six temperature sensors attached. The sensor locations are:

(1) Inlet: In the ducting, just before the SunLizard's inlet
(2) Outlet: In the ducting, just after the SunLizard's outlet
(3) Living area: Near the diagonally opposite corner of the loungeroom from the Sunlizard's outlet vent.
(4) Outside: Under the eaves, just outside the loungeroom window
(5) Under Floor: Under the loungeroom floor
(6) Roofspace: Above the loungeroom ceiling

The datalogger is set to send out a reading of each of these sensors every 30 seconds. The temperature data can be viewed and logged to a PC with the software provided.

Preliminary Test Results:

Some Temperatures observed on May 23rd, 2004

Time Outlet Temperature Living
Outside Under
Living Area
10:40am 41 33 16 18 16 18
11.40am 44 37 17 20.5 17 22
12:45pm 48 41 18 22 17 24
1:00pm 50 44 18 23 17 25
2:30pm 44 38 19 22 17.5 26

Note: The 'Outlet Temperature in Living Area' readings were taken with a normal household thermometer placed in front of the outlet vent. The other readings were taken using the datalogger.

Some observations:

Some further data can be seen here.

Notes: Experiences, Modifications, Short & Longer Term plans:


At present, the living area is not heating up as much as I had hoped it would. Or, perhaps it might be more correct to say that the area is heating up a little, but then cooling down more rapidly than expected. I think the main culprit is my house. I've done a few things such as:

- removing the 13 downlights and filling the holes they left in the ceiling
- replacing the batt insulation that was removed because of the downlights
- adding extra ceiling insulation to those areas that previously didn't have any
- removing the wall vents in each room and the ceiling vents in the kitchen, and patching-up the holes they left.
- Sealed a few other gaps around doors etc.

The modifications made so far have not made a huge improvement to the amount of heat retained in the living area. I've still got a few things I want to try though..

Cooling / Venting

I've installed a switch just outside the back door which lets me turn the fan on or off. This is not part of the original design. In the middle of the day during Summer, often the outside temperature was warmer than the temperature in the house. I didn't want the cooler air from within the house being vented, only to be replaced by warmer air from outside. The time that the venting would be of most use is after dusk, when the outside temperature has fallen below that inside the house. Unfortunately, the PV Panels won't provide any power to drive the fans at night.

There are a few possibilities here:

  1. Install a sealable vent in the floor. During Summer, this vent would be open, allowing the cooler air from under the house to be brought into the house.

  2. Use the PV Panel and a regulator to charge a small rechargable (Sealed Lead Acid or Gel Cell) battery during the day, and use this battery to power the fans at night.

  3. Use an appropriately sized 240 Volt power supply or plugpack to power the fans at night. This has the disadvantage of requiring extra power (usually from non-renewable sources), albeit only a relatively small amount compared with some other cooling options.


Also see the SunLizard Installation Notes & Photos page.

Last Updated: 25/07/04