Describes a simple device developed in the Institute for Applied Physics which is suitable for frrsh air control in air conditioned spaces. The protype instrument detects the amount of CO2 in the atmosphere on the basis of photoacoustics. Illustrates the device schematically and explains its operation.
States that in localities which must be ventilated by law such as cinemas, restaurants and assembly rooms of various kinds the fresh air supply is often greatly in excess of what is strictly needed. This excess air has to be transported, and possibly heated, cooled, humidified and dehumidified. Describes how controlling the air quality makes it possible to restrict the quantity of fresh air to the basic requirements, thereby keeping ventilation heat losses to a minimum. The control variable is the room air quality as monitored by a sensor.
Reports on some current projects in the UK using a certain type of CO2-controlled ventilation system, the "Builiding Breathaliser". This system has been installed in lecture theatres at the University of Kent, BHS department stores and cinemas owned by Rank leisure.
Notes the large savings possible if ventilation were adapted to the prevailing need. A promising possibility for indicating occupancy and thus the ventilation requirement is measuring the level of carbon dioxide. The project includes a test with equipment for CO2-monitoring of the exhaust air flow in an office building which controls the volume of outdoor air supply, thusmaintaining the CO2 level constant. Measures how the CO2 level can vary locally,how other pollutants in air can vary, how much energy can be saved.
Indicates that 35-70% of a building's annual energy consumption is used by ventilation plant. Notes difficulty in determining which energy saving measures are most profitable but states that restricting fresh air supply tothat required is one measure that has not been considered and that most systems are designed for maximum capacity without facilities for varying load according to conditions. Describes plant which uses CO2-controlled ventilation in a sports hall. Illustrates circadian changes.
Examines a new energy conservation technique based on the control of the "fresh air intake" through measurement of CO2 content in extracted air for different kinds of buildings. Assesses various techniques for measuring CO2 concentration in view to design a low cost sensor, concludes that theinfra-red absorption technique is the most suitable. Shows through computer simulation that a CO2 based ventilation system can provide a better pay-back period than an air-to-air heat exchanger.
Describes a system installed in the EKONO office building in Helsinki which allows the amount of CO2 in the exhaust air to control the ventilation rate. Uses a CO2 indicator, and adjusts the mixture of exterior and recirculated air so that the amount of CO2 during working hours is kept on ca 700 ppm. Describes use of equipment during winter 1981-82, when exterior air flow is registered. Measures the proportion of CO2 locally in order to study occasional variations that may occur. Studies the proportion of other pollutants in the room air with a gas chromatograph.
Describes a test carried out in the Fridley, MN, Junior High School Music Dept. to obtain air quality, energy and subjective response data on an Automatic Variable Ventilation System. Devises a control system with both CO2 and temperature inputs to control the use of outdoor air. Infiltration measurements lead to a quantitative measure of ventilation efficiency, which in turn lead to recommendations for air circulation patterns in rooms. The measured ventilation efficiency enables energy and CO2 models to fit measured data. Finds energy savings of approx. 20% in this application.
The heating system of a Junior High School in Minnesota has been re-equipped with a CO2-controlled variable ventilation system. The outdoor air dampers remain fully closed whenever the CO2 concentration is below a specified setpoint. During the early months of 1980, the system operated in alternate periods under the conventilanal temperature-driven control strategy and the experimental CO2-driven control strategy.
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