SE529210C2 - Ways to regulate the heating of a building at the intended level - Google Patents

Abstract

The present invention relates to a new method of controlling the heating of a building at a desired level. Firstly, building specific characteristics in the form of technical building characteristics and data on mode of operation of the building and building location are established, and meteorological parameters for the location of the building are forecast. Based on this a forecast equivalent temperature for the building is then calculated for chosen future points of time, such that there is a linear relation between heating power supply and the difference between the desired indoor temperature and said equivalent temperature. Finally, heat is supplied continuously in dependence of said difference.

Description

20 25 30 35 529 210 2 "Free heat", ie. the sum of solar heat supplements and internal heat, often results in temporary surpluses in the heat balance even during the heating season, especially in newer, well-insulated buildings with large glass surfaces. In traditional regulation, this leads to overtemperatures or the need for increased ventilation or even cooling. If you can instead take advantage of these free heating supplements, a significant proportion of the building's total heating needs during the heating season could be covered. When regulating the heat supply, the building's "inertia" (ie its mass and energy properties such as thermal insulation, tightness, etc.) are also taken into account, which means that a change in the internal balance balances the indoor temperature with some delay and damping. One way to do this is to reduce the supply of friends in advance of a future heat surplus and vice versa in the event of a heat deficit.

The core of the present invention is to utilize the 'free energies' in the regulation of building heating. This requires a forecast-based control method that is based on a calculation of the building's heat balance. In a more developed variant of the design, the thermal inertia of the building is also taken into account.

The present invention provides a new solution to the problem of maintaining the indoor temperature in a building by regulating the heat supply after a so-called 'Equivalent temperature' (ET), which is determined on the basis of the calculated net need for externally supplied heat. Wd calculation of ET takes care of the impact of the weather in such a way that the need for friends becomes a linear function of ET.

The invention solves the problem posed by designing it in the manner set out in the following independent patent claim. Other patent claims relate to advantageous embodiments of the invention. In the following, the invention will be described in more detail with reference to the accompanying drawings, where Figure 1 is based on operating data from a larger municipal district heating network and shows the daily sum of heating energy as a function of the daily average temperature, Figure 2 shows examples of control curves for flow temperature when controlling for a control temperature in the form of outdoor air temperature resp. equivalent temperature according to the invention and fi figure 3 shows a building's heating budget.

Figure 3 shows how the net need N of supplied energy for heating depends on your various items. N> 0 means heat deficit (heating demand) and N <0 means heat surplus. N can be expressed as N = c + / + / = + G-EP-s (1) where C is friend loss due to. transmission through the outer casing (roof, walls and windows), I is heat loss due to. natural features (inltration and exfiltration), F is loss of heat due to. fl genuine ventilation, G is heat loss to ground, EP is heat supplement from electricity use and people and S is heat supplement from solar radiation through windows. In a concrete calculation, one or more of the terms can of course be set to zero, if the term is negligible in relation to other teeth.

The calculation is based on calculating the individual items in eq. (1) and sums them to a net need of added or removed heat to maintain the desired indoor temperature. This net need is then expressed in terms of an equivalent temperature, ET, which can directly replace the prevailing outdoor air temperature as the governing parameter for the building's automatic control, even in a considerable control equipment. ET is defined so that the flow temperature is a linear function of the difference between ET and the desired indoor temperature, cf. Figure 2, which means a great advantage in the regulation.

ET is calculated on the basis of meteorological forecasts of temperature, wind and solar radiation. The latter parameter is calculated as a function of cloudiness, visibility, humidity and precipitation. For those who, unlike a person skilled in the art, are not familiar with this calculation, reference is made to Taesler, R. and Andersson, C., 10 15 20 25 30 35 529 210 4 1984: A method for solar radiation computations using routine meteorological observations, Energy and Buildings, Vol. 7 pp 341-352. The meteorological forecasts can advantageously have a time resolution of 1 hour. Of course, other time resolution can also be used.

When applying the invention, it is included to take into account both the basic technical data of the building and the building's method of use, as well as how the building's location and surroundings affect meteorological input data. You can do a completely individual calculation for each individual house or you can in many cases attribute the house in different respects to different typical cases. For example, all houses of a certain age and general construction can be assumed to have certain values of e.g. transmission through walls, ceilings and windows. The same applies to other aspects of the building.

To calculate forecast values at ET, one or fl of your data is used under each of the following headings: Building technical data o Data on the building's dimensions (length, width and height) o Data on thermal insulation (u-values) for roofs, walls, floors and windows o Data on the density of the building (dimensioning number of air changes per unit time) o Information on mechanical ventilation including information on the degree of heat recovery from exhaust air o Information on how much of each facade consists of window surfaces o Information on the main orientation of the house o Information on window light transmittance (transmission factor) o Information on the building's heat storage capacity (time constant).

Use of the building o Information on available internal friend during different times of the day for different days.

This refers to heat that is emitted from electrical or other appliances as well as from people. For a building, you can count on this addition individually, but often enough use case data depending on the building's use - housing, school, office, etc. o Information on the desired indoor temperature 10 15 20 25 30 35 529 1210 5 The information on building technical properties and methods of use is obtained by filling in an input form.

Location and surroundings of the building o Geographical data of the building (forecast point) o Information on building type and “ground roughness” in the vicinity of the forecast point (coefficient of friction for wind calculations) o Information on horizon shielding (of other buildings, heights, etc.) obtained via the above-mentioned input forms. Other information is established within the meteorological production process.

Meteorological parameters o Forecast values for outdoor air temperature o Forecast values for wind direction and wind speed o Forecast care for cloudiness, visibility, humidity and precipitation precipitation The meteorological parameters included in the model can be obtained in a known manner from normally available meteorological forecasts. To improve the accuracy, it is normally appropriate to correct the meteorological parameters with regard to the impact of the building's local environment - building type, “soil roughness” etc. It is well known to a person skilled in the art how this can be done and in the references to literature given in the following detailed description of the model, fi nns guidance for the untrained. In the following detailed description of the model for equivalent temperature, the net need N of heat according to eq. (1). The need for friends is assessed, as already stated, as being proportional to the difference between the desired indoor temperature and the equivalent temperature ET, i.e.

Nanvn-En wwm fi (3 which gives ET = n-Mm (æ 10 15 20 25 30 35 529 210 where N is the instantaneous net power requirement for maintaining the indoor temperature T, and k is specific to each definiated house type. The power requirement is calculated per m2 up- Equated (2) and (3) means that the flow temperature in systems with water-borne heat can be regulated along a single straight line with the slope k.

For each of the items in eq. (1) There are calculation methods which are well known to a person skilled in the art. The concrete calculation of the various parameters can thus take place in various known ways and does not form part of the basic idea of invention in the present case. For those who, unlike a person skilled in the art, are not familiar with these calculations, a brief presentation of a typical calculation is given below.

The different terms in eq. (1) is calculated for a single-cell building, ie. without regard to internal partitions or floor-separating floors. The indoor temperature is assumed to be the same throughout the building, usually = + 21 ° C. All terms are calculated as 1-hour values using observed or forecast meteorological data.

Heat transmission through walls and ceilings (term C) is calculated as C = u ,, AT, where AT = (T, - To) is the air temperature difference inside - outside and u, is an efficient, surface-weighted average of the heat transfer coefficients for the entire climate shell (walls, windows , tak) above ground. As input data for u-value calculation, you can use the building standard applicable to the building case or equivalent. Alternatively, individual data is used for the building. Data and calculation methods for this are given e.g. by Hagentoft, C-E., 2001: Introduction to building physics. Student Literature, Lund. See also Ashrae Handbook 1981 Fundamentals, American Association of Heating, Refrigerating and Air-Conditioning Engineers, inc., Atlanta.

Heat losses due to mechanical ventilation (term F) is also proportional to the temperature difference inside - outside, AT = (T, - To), and is calculated as F = nVp c, AT, 10 15 20 25 30 35 »529 210 7 where n is the number of air changes per hour, V is heated, ventilated volume, p is the density of the room air and c, is the specific heat capacitance of the air. Consideration is given to different degrees of ventilation day resp. night. The losses were reduced with regard to known or estimated efficiency (%) for heat recovery in the exhaust air.

The heat loss due to natural draft (term I) is calculated as I = f (AP) AT Vp c,, where f (AP) indicates the number of air revolutions per hour as a function of the pressure difference AP outside -in above the climate envelope. Necessary leakage factors are determined on the basis of normative air leakage in accordance with the building standard applicable to the year of construction or equivalent. The pressure difference depends on the temperature difference outside - inside (A7) and on the wind speed converted from the reference level 10 m above the ground to the ridge level and taking into account the building's wind exposure (impact from surrounding terrain and buildings and orientation relative to wind direction). Theory and methods that can be used for the conversion to the roof ridge level are found in e.g. Cook, NJ, 1985: The designers guide to wind loading of building structures, part 1, Building research establishment (BRE) Garston, Buttenivorths, London och Plate, EJ, 1971: Aero- dynamic characteristics of atmospheric boundary Iayers, AEC critical review series , National technical information service, US dep. of commerce, Spring fi eld, Virginia.

For calculating the wind pressure, form factors (pressure coefficients) are used for each sub-surface of the climate envelope. Further information can i.a. obtained from AlVC, 1984.

Wind pressure data requirements for air in fi ltration calculations, Technical Note AlC 13, Air in fi ltration Center, Bracknell eller Wirén, B., 1985: E fi ects of surrounding buildings on wind pressure distributíons and ventilation Iosses for single-family houses. Part 1: 1 ßé-storey detached houses, M 85:19, Statens institut för byggnadsforskning, Gävle.

The calculation of the function f (AP) is reported in detail iTaesler, R., 1986: Climate, buildings and energy exchange - an integrated approach. Technical messages no. 297, inst. for heating and ventilation technology KTH, Stockholm. Regarding models and methods for deduction calculation, see e.g. Ashrae Handbook 1981 Fundamentals, American Association of Heating, Refrigerating and Air-Conditioning Engineers, lnc., Atlanta or Herrlin, M.K., 1992: Air-flow studies in multizone 10 15 »20 25 3D 35 529 210 8 buildings. Models and applications, Dep. of building services engineering KTH, Swedish council for building research, Stockholm.

Heat loss to ground (tin G) is a small item and can be approximated as constant and proportional to the difference between the indoor temperature (T is the heat transfer coefficient for the basic structure against the ground. heat supply from electricity use and people (tin EP) depends on the building's area of use and mode of operation. The heat supplement can be calculated or estimated. Estimated values can be determined from the National Board of Housing, Building and Planning, 1994: Buildings' friend energy needs, starting points for redistribution calculation, Handbook, National Board of Housing, Building and Planning, Karlskrona.

The solar protection supplement (term S) is calculated on the basis of calculated direct and diffuse solar radiation towards the respective façade surface with regard to the orientation of the building and the horizon cut-off of the surroundings. The calculation is reported in detail iTaesler, R. and Andersson, C., 1984: A method for solar radiation computations using routine meteorological observations. Energy and Buildings, Vol. 7 pp 341 -352. The solar heat supplement is obtained after the calculated radiation towards the window has been reduced with regard to the windows' transmission capacity (2- or 3-glass) and possibly fixed sun-shielding devices (blinds etc.). Required transmission factors can include retrieved from Brown, G. and lsfält, E., 1974: Soiín radiation and solar sensing, Report R 19: 1974, Statens råd för byggnadsforskning, Stockholm.

The above leads to the following equation for the net requirement NN = (msxißixtir + e - EP - s (4) The coefficients A and B are determined by multiple regression on equ. (4) using weather data for a longer period, for example a full year hourly Each individual building and each type house case is characterized by the values of the regression coefficients A and B. One and the same combination of meteorological data (T, v, S) thus gives different values of ET depending on the building properties and position (exposure).

Eq. (2) and (3) now give the following expression for the equivalent temperature ET: Er = T- (1 / A) xrßm / * XAT + G-EP - s) (5) Eq. (5) means that ET can be either higher or lower than the air temperature T depending on whether the “free energies” (friend supplements EP + S) are greater or less than the losses due to wind and temperature. Net need for heat exists when ET <T, -.

If you want to utilize the building's heat storage capacity (inertia), the supply of friends must be controlled with foresight. The inertia of the building is usually indicated by a time constant. For those who, unlike a professional in the field, are not familiar with the calculation of this time constant, which takes place on the basis of technical data for the building, reference is made to Petersson, B-Å., 2001: Applied building physics, Student Literature, Lund.

The inertia can be taken into account by partly equalizing the forecast, momentarily equivalent temperature with weight coefficients calculated with regard to the building's time constant, and partly by introducing a shift in the time course of the equalized equivalent temperature. The time delay is usually 1-3 hours.

A brief theoretical account of consideration for the building's inertia follows below.

The need for extremely supplied heat at time t for maintaining the desired indoor temperature, taking into account the heat dissipation or heat absorption of the building frame, is N '(f) = NIf) + AN fl) (6) The corresponding equalized equivalent temperature is ET' (t) = ET (t) AET (t) (7) 529 210 10 An expression for AET (t) can be derived as follows. An exponential increase or decrease of heat stored in the building by the amount AN (t) over the time interval 6 gives a corresponding change in the equalized equivalent temperature by 415m) went) e ** / '(1-e ~ * / f) <8 ) where r is the time constant of the building.

The equalized equivalent temperature at time to is then Erna) = Erna) + XAETKt), I = -f ie. 10- Erïfa) = Erna) + íAEï (t) e "'ff (1-e" lf) (9) t = -f Ekv. (9) can be written as ET '(r ,,) -_- ET (f ,,) - yET (f ,,) + ïa fl rysrçg, -f) (10) I = -f where pïagß) and a (f) = e ~ fff (1-e ~ * ff) (11) t == - f The coefficient y and the time constant 1 are related by glue, _ ,,,, y = 1- 1 / e = 0.632.

Corresponding values of 7 and r are given in the following table Time constant r Coefficient y 6 hours 0.535 24 hours 0.606 48 hours 0.619 72 hours 0.623 Applied values in the interval 12 <r <24 hours. t) 1D 155 213 2: 5 30 529 210 11 The effect of eq. (9) is to provide a momentarily unbalanced heating budget. During periods of declining ET ', the heat supply becomes insufficient to cover the total loss and vice versa during periods of rising ET'. The equalization reduces variations in heat output, especially power peaks, but on the other hand tends to cause a deviation in the indoor temperature from the desired, constant value. This tendency is counteracted by a decrease or an increase in the stored heat in the building. To keep the indoor temperature within acceptable limits, the time constant in eq. (9) not selected too large.

To control the effect of heat storage on the daily variation in indoor temperature, the equivalent temperature ET 'according to eq. (9) is further modified as follows.

Emm) = E1 "(f.,) + Aerragetfif” (12) where AETm) = Eeifo + 61) - ETUO) (13) The time step å * gives rise to a phase shift forward. The daily energy balance is not affected by this.

The method according to the invention can of course be used in new control systems, but also in already installed control systems. In both cases, the outdoor temperature is replaced by the equivalent temperature during regulation.

In concrete terms, values are calculated for the equivalent temperature, which is based on e.g. on meteorological forecasts, by someone who can perform such, e.g. SMHI, and distributed to subscribing customers as data files for use in the control equipment in their buildings. For practical reasons, forecast data is sent for a number of days ahead, usually 5 days, but other periods are of course conceivable.

Claims (8)

10 15 20 25 30 5 529 210 12 Patent claims: Method of regulating the heating of a building at the intended level, characterized in that building-specific data are determined for the building in the form of building technical data and data on the building's use and location, that meteorological parameters are forecast for the building's location, that based on the building-specific data and the meteorological parameters calculate a forecast equivalent temperature for the building at selected future times, such that there is a linear relationship between the added heat effect and the difference between the desired indoor temperature and the said equivalent temperature and that heat is continuously added of said difference between the desired indoor temperature and said equivalent temperature. 2. A method according to claim 1, characterized in that the meteorological parameters are corrected with regard to the impact of the building's local environment and the thus corrected meteorological parameters are used in the calculations of the forecast equivalent temperature. 3. A method according to claim 1 or 2, characterized in that the inertia of the building is taken into account by equalizing the time course of the equivalent temperature with regard to the time constant of the building. 4. A method according to any one of claims 1-3, characterized in that the inertia of the building is taken into account by introducing a displacement of the time course of the equivalent temperature. 5. A method according to any one of claims 1-4, characterized in that the building technical information comprises one or more of the following information, namely information on the dimensions of the building, information on the thermal insulation of its roof, walls, floor and windows, information on the tightness of the building, information on the degree of heat recovery from the building's effluent air, information on the proportion of window space on the building's respective facade, information on the building's main orientation, information on the window surfaces' transmission factor and information on the building's heat storage capacity. 10 5 529 210 13 A method according to any one of claims 1-5, characterized by the poisons if the use of the building comprises one or more of the following information, namely information on available indoor heating at different times of the day for different days from persons and heat generating appliances and an indication of desired indoor - temperature. a v to upp- 7. A method according to any one of claims 1-6, characterized in that the information on meteorological parameters for the location of the building comprises one or more of the following data, namely forecast values for outdoor air temperature, forecast values for wind direction and wind speed and forecast values for cloudiness, visibility, humidity and precipitation. 8. A method according to any one of claims 2-7, characterized in that the information about the building's local environment comprises one or more of the following information, namely information about the surrounding building type, ground roughness for local wind calculations and information about horizon shields around the building depending on buildings and natural heights.