facts about solar warm air...
There is good reason to be critical when considering construction and if you are told that a system has an “extremely high output”
A solar air collector’s technical construction looks simple and can actually be relatively easy to copy. However, there are surprisingly many pitfalls and the risk of construction errors is high.
As a well-established manufacturer, SolarVenti Ltd. welcomes new competitors as long as the competing product is well constructed and will provide a durable and good experience for the user.
Unfortunately, we regularly see manufacturers - both in Denmark and abroad - who develop solutions that are badly thought through and who run misleading marketing campaigns in an industry that is still relatively young.
Both ill-considered solutions and misleading marketing campaigns damage the industry as a whole as both have a negative impact on a customer’s trust. Regardless of the solar air collector you, the customer, end up choosing, there are a few basic things that are worthy of note when you read product descriptions and other sales material.
The main benchmark for the evaluation of the efficiency of a solar air collector will always be the number of cubic meters of incoming air per hour at a given temperature. Claims of, e.g., “250 % higher output than similar products” are beyond the realms of current technology and, therefore, technically impossible, but are also an example of misleading marketing.
The fundamental principle behind efficient dehumidification, ventilation and supplementary heating from a solar air collector is that the collector blows large volumes of air into the house at a temperature that is optimal in relation to the volume of air.
The heat from the sun is used, out in the panel on the roof or wall, to adjust the temperature of the air that is blown into the house so that it is close to - and generally above - the indoor temperature of the house.
In this way, the house is supplied with automatic and cost-free dehumidification and ventilation, which usually results in noticeable savings on electricity and heating bills as well as a good indoor climate.
In brief: A well-constructed solar air collector blows large volumes of air, at a temperature adjusted to be as high as possible, into the house when the sun shines. A solar air collector’s output of a given temperature must always be quoted together with the number of cubic meters of incoming air per hour - otherwise the quoted temperature is of no value as product data.
Today, it is standard for the modern solar air collector to have the electricity-producing solar cell built into the actual panel. The solar cell fits discretely into the panel and is well protected against thrown-up pebbles and other types of impact.
And the solar cell relinquishes its own heat to the solar air collector panel and, thus, into the house rather than into the air outside, for the benefit for the birds.
The protected position of the solar cell within the panel imposes demands on the “self-cooling” properties of the system. Temperatures of up to 140 degrees Celsius can be reached inside the panel when the system is switched off and the fan is not running. Neither the solar cell nor the fan can cope with temperatures of this magnitude. Therefore, it is essential that the solar air collector is able to cool itself when it is switched off - i.e. when the fan is not working.
Self-cooling of the solar air collector by means of an extra fan which blows air from inside the house through the solar panel when the system is switched off is not a good solution - for several reasons. Firstly, and most importantly, used air from inside the house that is blown out through the panel will always result in deposits of organic material inside the panel in the long term.
This means that either the customer himself or a service technician will have to remove, dismantle and clean the whole panel on the inside at some point: a large and time-consuming job, regardless of whether it needs to be done after six months or after three years.
Another reason why the extra fan inside the solar air collector panel is a bad solution is that there will always be noise from the system when the sun shines - and it is not possible to switch the noise off!
A third reason is that the solar cell in a panel with a separate cooling fan will overheat and be destroyed if, by unfortunate coincidence, the extra fan/solar cell/cable or regulator does not work for some reason or other.
Briefly: A solar air collector’s self-cooling system must work in all situations - without being heard. And it is never a good idea to blow used air from the house through a solar air collector panel. A solar air collector panel must be clean on the inside and remain so.