System for improving both energy efficiency and indoor air quality in buildings

Abstract

A building's Heating Ventilating and Air Conditioning (HVAC) system is made more energy efficient and the indoor air quality (IAQ) of the building's circulating air is improved by incorporating a greenhouse as an integral part of the HVAC system and by utilizing a novel feed forward control strategy that maintains the proper levels of temperature, humidity and CO2 concentration in the building under varying conditions of day, time, use and occupancy.

Description

DESCRIPTION OF DRAWINGS

FIG. 1 Side view schematic of a school building HVAC system with a greenhouse.

FIG. 2 Front view schematic of a school building HVAC system with a greenhouse.

FIG. 3 Piping schematic of a school building HVAC system with a greenhouse.

FIG. 4 a Graph of the variation of the classroom temperature for a typical school day.

FIG. 4 b Graph of the variation of the hot water flow to the classroom radiators for a typical school day.

FIG. 5 a Graph of the variation of the humidity of the classroom air for a typical school day.

FIG. 5 b Graph of the humidity of the inlet air to the classroom for a typical school day.

FIG. 6 a Graph of the variation of the CO₂ level in the classroom for a typical school day.

FIG. 6 b Graph of the variation of the inlet air flow into the classroom for a typical school day.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THIS INVENTION

Using a school building as one example of a type of structure that can be used in the preferred embodiment of this invention, refer to FIGS. 1, 2, 3, 4a, 4b, 5a, 5b, 6a, 6b. For a school building (1) starting on Monday morning during the heating season, the empty classrooms (2) would be at a lower temperature and humidity with minimum circulating air flow. The building air circulation rate, the exhaust air rate and the inlet air rate of the HVAC system (3) would be minimal with low energy consumption. At a preset time before school starts, the computer controller (4) signals the HVAC system (3) to adjust the hot water flow control valve (5) to increase the flow of hot water to the radiators (6) to raise the temperature in the classrooms (2). At the control hot water flow rate, the temperature in the classrooms (2) is below the target value. As teachers and students arrive and the room is being occupied the temperature, humidity and CO₂ in the classroom (2) will increase due to the body heat and respiration of the occupants. As the temperature in the classrooms (2) begins to increase, due to the arrival of more and more students, the slope of the temperature curve is used by the algorithms in the computer controller (4) to determine how much to throttle back on the hot water flow to the radiators (6) to prevent overshooting the temperature target. When equilibrium is obtained, the hot water flow rate remains relatively constant until the class is dismissed at the end of the school day. The computer controller (4) then reduces the hot water flow rate and the classroom (2) is allowed to cool down to the nighttime lower target temperature to conserve energy. (See FIGS. 4a and 4b). If a hot air heating system is used instead of a hot water heating system, the same principles are used except instead of controlling the hot water flow the temperature and flow of the hot air is controlled.

In a similar manner with the arrival of the students, the humidity and CO₂ concentration of the air in the classrooms (2) will increase. The slope of the humidity and CO₂ concentration curves are used by the computer controller (4) to regulate the humidity and the flow rate of the circulating inlet air to the classrooms (2). The circulating air flow into the classrooms would increase fairly rapidly as the occupants increase because of the sudden rise in the CO₂ concentration in the air in the room. The airflow into the room would throttle back as it approaches the target levels for CO₂ and humidity and then would be fairly constant when equilibrium is obtained. At the end of the school day when the children are dismissed,.the circulating airflow to the classrooms (2) would be reduced to the lower nighttime settings to conserve energy. The circulating airflow rate is primarily controlled by varying the speed of the air circulating fans (7). Preferably these fans would have different capacities to extend the controllable air circulation rate from very low when the building (1) is unoccupied to much higher rates when the building (1) is fully occupied. The classroom (2) air flow control dampers (8) are mainly used to trim the airflow to the classrooms (2) or to minimize airflow to low occupancy classrooms (2) or to seal off empty classrooms (2) during the school day to reduce unnecessary circulating airflow through low occupancy or empty classrooms (2) thereby saving energy (see FIGS. 5a, 5b, 6a and 6b).

The temperature sensors (9), humidity sensors (10) and CO₂ sensors (11) related to the classrooms (2) continuously transmit data to the computer controller (4), which also receives data on temperature, humidity and CO₂ from sensors in the exhaust air ducts (12), the recycle air duct (13) and HVAC inlet air duct (14) as well as from the greenhouse (15) and ambient air (16) in order to continuously update the control parameters to maintain high quality indoor air and minimize energy consumption. At night and before the school day starts, the circulating airflow rate is very low, the fresh makeup air flow rate from the greenhouse is very low and the exhaust air flow rate, which is equal to the makeup air rate, is also very low and a high proportion of the circulating air is being recycled through the recycle air duct (13). As the classrooms (2) begin to be occupied and the concentration of the CO₂ in the exhaust air from the classrooms increases the speed of the air circulating fans (7) increase and the inlet air flow control damper (17) opens wider to increase the flow of fresh air from the greenhouse (15) by way of the inlet air two-way proportioning damper (18) and inlet air duct (14) and the variable speed exhaust fans (19) increase speed and the exhaust airflow control damper (20) opens to increase the flow of exhaust air through the exhaust air duct (12) and out of the exhaust air two-way proportioning damper (21) into the greenhouse (15) and the recycle airflow control damper (22) closes down to reduce the amount of recycled air. At the end of the school day, the process is reversed and the fan speeds and damper settings will slope back to the nighttime settings to conserve energy.

In the greenhouse (15), the exhaust air from the building (1), containing a high level of CO₂ and possible airborne pollutants such as volatile organic compounds (VOC), is directed to the lower ground level where selected species of plants (23) are grown which remove the CO₂ and pollutants from the exhaust air. The plants (23) use the CO₂ and water and nutrients from the soil for growth and in combination with the bacteria in the soil around the roots of the plants (23) transform the pollutants into harmless compounds. The photosynthesis process in the selected plants (23) takes up the CO₂ and emits oxygen into the air and the selected plants (23) also have the ability to emit beneficial negatively charged ions into the air. The oxygenated air containing the beneficial negatively charged ions is less dense than the CO₂ laden exhaust air and will tend to rise in the greenhouse. The opening to the inlet air duct (14) to the building (1) is therefore placed higher and at the opposite side of the greenhouse (15) to reduce intermingling of the exhaust air with the fresh makeup air to the building (1).

During periods of low light or at night, high efficiency sunlamps (24) can be activated to improve plant growth and to extend the time available for CO₂ and pollutant removal. As a further refinement an inlet air two-way proportioning damper (18) can be utilized to divide 0 to 100% of the inlet makeup air to the building between the greenhouse (15) and the ambient air (16). Similarly an exhaust air two-way proportioning damper (21) can be utilized to divide 0 to 100% of the exhaust air from the building into the greenhouse (15) or the ambient air (16). The decision on whether to turn on the high efficiency sunlamps (24) or use the inlet air two-way proportioning damper (18), and exhaust air two-way proportioning damper (21) or any combination is determined by the algorithms in the computer controller (4).

The algorithms in the computer controller will continuously calculate what settings to use for the hot water flow control valves (5), the inlet air flow control dampers (17), the exhaust air flow control damper (20) and the inlet air controllable two-way proportioning damper (18), the exhaust air controllable two-way proportioning damper (21), as well as the speeds of the variable speed air circulating fans (7) and variable speed exhaust air fans. (19) The settings on all the controllable equipment are adjusted so as to insure that the CO₂ concentration and the air quality in each of the classrooms (2) are at a high standard and the temperature and humidity targets are being achieved using the lowest practical total energy consumption based on the sum of the energy used by all the equipment in the entire system.

FIG. 4 a represents a graph of the variation of the temperature of the classrooms (2) during a typical school day. FIG. 4b represents a graph of the hot water flow to the radiators (6) in the classrooms (2) during a typical school day. FIG. 5a represents a graph of the variation of the humidity of the classrooms (2) during a typical school day and FIG. 5b represents a graph of the humidity of the inlet air flow to the classrooms (2) for a typical school day. FIG. 6a represents a chart of the variation of the CO₂ level of the air in the classrooms (2) during a typical school day. FIG. 6b represents a graph of the variation of the inlet air flow into the classrooms (2) for a typical school day.

On weekends and holidays, all of the parameters default to the nighttime settings when the classrooms (2) are not occupied. The same basic control strategy is used in the offices (25) and the gymnasium/cafeteria (26) and other zones of the building (1). During the cooling season the same strategy is used except for cooling rather than heating.

The airflow indicators (27) throughout the system aid in establishing empirical values required by the algorithms in the computer controller (4) and for troubleshooting operational problems that may come up due to mechanical failures or other causes.

Claims

1. An HVAC system for buildings and other structures consisting of traditional HVAC components in conjunction with a greenhouse as in integral part of the system consisting of: a) a heating humidification section (oil, gas, coal, wood, electric, heat pump, geothermal, solar or any other type)b) an air conditioning section (air conditioner, heat pump, geothermal or any other type)c) Fans or any other type of air movers, preferably variable speed, for air circulation, exhaust air and inlet air.d) Air circulating ductwork with appropriate air filters and grilles.e) Controllable dampers and valves.f) Individual room radiators (optional).g) Sensors for temperature, humidity, CO2, air flow, hot water flow and for any heating and cooling medium flows.h) A computer or any other type of programmable controller with algorithms to minimize air circulation rates, exhaust air rates and inlet air rates while maintaining the desired targeted room temperatures, humidity and CO2 levels which will normally vary depending on day, time, use and occupancy.i) An attached or separate greenhouse with appropriate ductwork to accept 0 to 100% of the building exhaust air and a means to supply 0 to 100% of the building's supply air requirements.j) Selected plants in the greenhouse that have the ability to absorb CO2 and other air pollutants at a high rate and plants that have the ability to emit oxygen and beneficial negatively charged ions into the air at a high rate. All of the above components are not necessary to practice the teachings of this patent.

2. A system of claim 1 whereby the greenhouse preferably has an enclosed volume of more than two times the design hourly flow of the building exhaust air.

3. A system of claim 1 whereby the greenhouse preferably has a plant growing area of more than 4 square feet for each 100 cubic feet of design hourly flow of building exhaust air.

4. A system of claim 1 where greenhouse plants are selected on the basis of high CO2 and other pollutant uptake rates and their ability to emit oxygen and beneficial negative ions and for their commercial value or any combination. Typically these are leafy fast growing plants, trees, fruits or vegetables and preferably where the leaves have a large total surface area and account for a large portion of the above ground biomass of the plant.

5. A system of claim 1 whereby plants suitable for this purpose but not limited to are as follows:

6. A system of claim 1 whereby at night or during periods of low light or for any other reason when the CO2 concentration of the greenhouse air available for inlet air makeup air to the building HVAC system is too high, high efficiency sunlamps can be turned on to enhance or extend the conditions for plant growth thereby increasing the rate of CO2 removal from the greenhouse air and increasing the rate of O2 and beneficial negatively charged ions addition into the greenhouse air.

7. An HVAC system of claim 1 whereby sensors for measuring temperature, humidity, CO2 airflow and the flow of any other heating or cooling medium are located strategically throughout the system and continuously transmit the values of each of the parameters to a central computer controller where algorithms are stored and continuously updated to determine the slope of the curves for the changes in temperature, humidity and CO2 levels in the building and in the greenhouse.

8. A system of claim 1 and 7 whereby the slope or the rate of change in any measured parameter is used to control the rate of any of the controllable factors such as air flow or other fluid flows, the temperature of the air and other fluids, the humidity of the air and the CO2 level of the air.

9. A system of claim 1 and 7 whereby algorithms in the controller determine the regulation priorities so as to maintain the proper temperature, humidity and CO2 levels at the lowest air circulation rate, lowest air exhaust rate and lowest makeup air rate to improve energy efficiency so as to maintain good air quality using the lowest practical total energy consumption based on the sum of the energy used by all the components in the entire system.

10. A system of claim 1 and 7 whereby the desired temperature, humidity and CO2 level is used as a feed forward target and not as a set point subject to overshooting, undershooting and cycling which leads to occupant discomfort and lower energy efficiency.

11. A system of claim 1 and 7 whereby the amount of the building exhaust air discharged into the greenhouse is controlled at the minimum rate required to maintain the ASHRE recommended CO2 level in the air in each room of the building or preferably below 0.4%. Preferably the exhaust air is directed to the lower portion at one end of the greenhouse so that the higher density CO2 in the exhaust air comes quickly in contact with the ground level plants stimulating faster removal of the CO2 and pollutants from the exhaust air, encouraging faster growth of the plants and promoting more emissions into the air of oxygen and beneficial negatively charged ions by the plants.

12. A system of claim 1 and 7 whereby the amount of makeup air from the greenhouse to the building's HVAC system is controlled at the minimum necessary to maintain the desired ASHRE recommended CO2 level in the air of each of the rooms of the building or preferably below 0.4%. Preferably the makeup air to the building is drawn from the upper portion of the opposite end of the greenhouse from the exhaust air inlet so that the lighter density lower CO2 and higher oxygenated air containing beneficial negative ions is drawn into the building's HVAC system.

13. A system of claim 1 and 7 whereby the air circulation rate and the flow rate of any other heating and cooling fluid in each of the rooms is controlled at the minimum necessary to maintain the proper temperature, humidity and CO2 level dependant on day, time, use and occupancy.

14. A system of claim 1 and 7 where a two-way proportioning exhaust damper is used so that when ambient air conditions of temperature, humidity or CO2 level may be beneficial, a portion or all of the exhaust air from the building can be divided between the greenhouse and the ambient air.

15. A system of claim 1 and 7 whereby a two-way proportioning inlet damper is used so that when ambient air conditions of temperature humidity and CO2 levels are beneficial all or any portion of the inlet air to the building can be drawn from the greenhouse and ambient air.