Ventilation unit, system and method
A ventilation unit is for ventilating an indoor space, and incorporates an air cleaning device and mechanical restrictor for controlling a restriction to a flow resulting from a pressure differential across the unit. There is determination of the inside and outside air pressures in the vicinity of the unit and of air quality parameters inside and outside. The air cleaning device and the mechanical restrictor are controlled in dependence on the determined air pressures and air quality parameters. This provides a fan-less, and hence low-power ventilation unit, which relies on throttling the natural air flow across the unit to provide flow control, and hence enable control of air quality. The air cleaning device may be operated only when the flow is into the inside space, saving power.
1. A ventilation unit for ventilating an indoor space by natural ventilation, the ventilation unit comprising:
a first air port for positioning outside the indoor space;
a second air port for positioning inside the indoor space;
an air cleaning device between the first and second air ports;
a mechanical restrictor for controlling a restriction to a flow between the first and second air ports, wherein the flow results from a pressure differential between the first and second air ports;
a pressure sensing arrangement for determining air pressures or an air pressure difference in the vicinity of the first and second air ports;
a first air quality determination system for determining air quality parameters relating to a space outside the indoor space;
a second air quality determination system for determining air quality parameters relating to the indoor space; and
a controller,
wherein the controller is adapted to:
control the mechanical restrictor in dependence on the determined air pressures and air quality parameters; and
control the air cleaning device in dependence on the determined air pressures and air quality parameters and in response to a determination that the flow, resulting from the pressure differential between the first and second air ports, is into the indoor space.
2. The ventilation unit as claimed in claim 1 , wherein the air quality parameters comprise temperature and relative humidity.
3. The ventilation unit as claimed in claim 1 , wherein the air quality parameters comprise a particle pollution level.
4. The ventilation unit as claimed in claim 1 , wherein the controller is further adapted to:
implement a minimum flow restriction when the air quality parameters relating to the space outside the indoor space meet a first set of indoor air quality requirements; and/or
implement a maximum flow restriction when the air quality parameters relating to the space outside the indoor space meet a second set of indoor air quality requirements.
5. The ventilation unit as claimed in claim 1 , wherein the controller is further adapted to implement the control of the flow restriction to provide a number of air changes per hour of the indoor space which falls within a set range.
6. The ventilation unit as claimed in claim 1 , wherein the air cleaning device comprises an electrostatic air cleaning device which comprises:
a particle charging section;
a particle precipitation section, comprising parallel electrode plates; and
a source of electric potential for applying a voltage between adjacent electrode plates in the particle precipitation section.
7. The ventilation unit as claimed in claim 6 , wherein the electrostatic air cleaning device further comprises a current sensor for measuring an electric current flowing through the parallel electrode plates, and wherein the controller is further adapted to determine a level of particle precipitation from the measured electric current flowing through the parallel electrode plates.
8. The ventilation unit as claimed in claim 1 , further comprising an output device for providing an output relating to one or more of:
a contamination status of the air cleaning device;
the air quality parameters relating to the space outside the indoor space; and
the air quality parameters relating to the indoor space.
9. A ventilation system, comprising:
a plurality of ventilation units each as claimed in claim 1 ; and
a communications system for enabling communication between the controllers of each ventilation unit thereby to enable coordinated control of the ventilation units.
10. The ventilation unit as claimed in claim 1 , wherein the controller is further adapted to:
implement a minimum flow restriction when indoor air quality relating to the indoor space is lower than outdoor air quality relating to the space outside the indoor space; and
implement a maximum flow restriction when the indoor air quality is higher than the outdoor air quality.
11. A method of ventilating an indoor space by natural ventilation using a ventilation unit of a ventilation system between the indoor space and an outside space, the method comprising:
determining air pressures in, or an air pressure difference between, the indoor space and the outside space in the vicinity of the ventilation unit;
determining air quality parameters in the outside space;
determining air quality parameters in the indoor space;
determining that a flow across the ventilation unit, resulting from a pressure differential between the indoor space and the outdoor space, is into the indoor space;
controlling a restriction to the flow across the ventilation unit, resulting from the pressure differential between the indoor space and the outside space, in dependence on the determined air pressures and air quality parameters; and
controlling an air cleaning device of the ventilation unit in dependence on the determined air pressures and air quality parameters and in response to determining that the flow across the ventilation unit, resulting from the pressure differential between the indoor space and the outside space, is into the indoor space.
12. The method as claimed in claim 11 , wherein the air quality parameters comprise temperature, relative humidity, and a particle pollution level.
13. The method as claimed in claim 11 , further comprising:
implementing a minimum flow restriction when the air quality parameters relating to the outside space meet a first set of indoor air quality requirements; and
implementing a maximum flow restriction when the air quality parameters relating to the outside space meet a second set of indoor air quality requirements.
14. The method as claimed in claim 11 , further comprising implementing the control of the flow restriction to provide a number of air changes per hour of the indoor space which falls within a set range.
15. The method as claimed in claim 11 , further comprising providing communication between multiple ventilation units of the ventilation system thereby to enable coordinated control of the ventilation units.
16. The method as claimed in claim 11 , further comprising:
implementing a minimum flow restriction when indoor air quality relating to the indoor space is lower than outdoor air quality relating to the outside space; and
implementing a maximum flow restriction when the indoor air quality is higher than the outdoor air quality.
17. A computer program comprising computer program code means which is adapted, when said computer program is run on a computer, to implement the method of claim 11 .