Calculation Method for evaluating Solar Assisted Heat Pup Systes in SAP 2009 15 July 2013 Page 1 of 17
1 Introduction This docuent describes how Solar Assisted Heat Pup Systes are recognised in the National Calculation Method for Energy Rating of Dwellings, known as SAP 2009. Below is a siplified energy flow diagra of a Solar Assisted Heat Pup Syste, which includes the following principal coponents: Solar theral heat collector/abient heat absorber Water-to-water heat pup Theral store Low teperature theral store Note: the diagra only shows the ain energy flows and not actual connections. Energy flow scheatic C/H 35ºC DHW In-line heater Solar theral collector Theral store Teperature 38ºC or higher Heat pup heats theral store to 38ºC Low teperature theral store Teperature 20ºC to -5ºC Solar theral collectors ebedded in roof tiles capture insolation on war sunny days, whilst absorbing abient heat fro surrounding air at night and during overcast periods. Captured solar energy is fed to: a) the theral store, when the solar-heated water is war enough, or b) the low teperature theral store otherwise Heat absorbed by the collector at night or on overcast days fro the environent is fed to the low teperature theral store. A water-to-water heat pup transfers heat fro the low teperature theral store to the theral store when requested by the control syste. Page 2 of 17
Doestic space heating and hot water services are provided by puping Priary Water fro the theral store to two separate plate heat exchangers, where heat is transferred to the doestic space heating syste or to a separate ains pressure hot water syste that has a suppleentary direct electric inline heater. For the purposes of analysis in SAP, the operation of the syste has been divided into four odes. Mode 1 (day tie war and sunny) Defined as the daylight hours (hours between sunrise and sunset) when the air teperature exceeds 15ºC and horizontal direct and diffuse insolation exceeds 10W/ 2. In this Mode: - Solar energy is captured and delivered to the theral store to offset hot water heating load. Any shortfall is et by the electric inline heater. - The heat pup does not operate. Mode 2 (day tie cool and sunny) Defined as the daylight hours when the air teperature is 15ºC or below and horizontal direct and diffuse insolation exceeds 10W/ 2. In this Mode: - Solar energy is captured and delivered to the low teperature theral store - The heat pup upgrades heat fro the low teperature theral store to the theral store. The heat source for the syste is the outside air and solar energy cobined; an average source teperature of 10 C is assued. The sink teperature is 38ºC (or suitable set-point defined by Manufacturer). - The theral store supplies heat to the hot water and space heating systes. Any shortfall in water heating load and space heating load is et by separate direct-electric inline heaters. Mode 3 (day tie cool and overcast) Defined as the daylight hours when the air teperature is 15 C or below and direct and diffuse insolation is 10W/ 2 or below. In this Mode: - The solar collector absorbs abient heat and delivers it to the low teperature theral store. - The heat pup upgrades heat fro the low teperature theral store to the theral store. The heat source for the syste is the outside air; an average source teperature of 4.5 C is assued. The syste operates siilarly to an Air Source Heat pup in this ode. The sink teperature is 38ºC (or suitable set-point defined by Manufacturer). - The theral store supplies heat to the hot water and space heating systes. Any shortfall in water heating load and space heating load is et by separate direct-electric inline heaters. Mode 4 (night-tie) Defined as the hours when not in ode 1, 2 or 3. In this Mode: - The solar collector absorbs abient heat and delivers it to the low teperature theral store. - The heat pup upgrades heat fro the low teperature theral store to the theral store. The heat source for the syste is the outside air; the low teperature theral store is assued to be 5 C below the outside air teperature giving an average source teperature of -1.2 C. The syste operates siilarly to an Air Source Heat pup in this ode. The sink teperature is 38ºC (or suitable set-point defined by Manufacturer). - The theral store supplies heat to the hot water and space heating systes. Any shortfall in water heating load and space heating load is et by separate direct-electric inline heaters. Page 3 of 17
Any shortfall in space heating is deterined by the capacity of the heat pup or rate of heat transferred to the low teperature theral store, whichever is the sallest. The theral store is assued to supply heat for space heating first, with any reaining heat supplied to the doestic hot water service. 2 Basis of the ethod The basis of the Solar Assisted Heat Pup calculation ethod is to analyse the Mode 1 operation within a separate suppleentary calculation procedure (Appendix workbook). The other odes of operation (Modes 2 4) are odelled as a standard heat pup, see SAP 2009 Appendix N, but with odified average source and sink teperatures as noted above and in accordance with EN15316. The Plant Size Ratio (PSR) range is also extended to 5.0, where the Product Characteristics Database (PCDB) records values at: 0.2, 0.6, 1.0, 2.0, 3.0, 4.0 and 5.0. The additional heat losses associated with Solar Assisted Heat Pup systes in coparison to standard types (i.e. air, ground or water source) are also odelled within the suppleentary calculation procedure (Appendix ) for all operating odes. 2.1 Mode 1 The suppleentary calculation procedure (Appendix ) calculates the direct reduction in water heating due to captured solar energy when the air teperature exceeds 15ºC and direct and diffuse solar insolation exceeds 10W/ 2. To siplify the calculation process (Appendix ) for Mode 1 operation, a reference syste was defined to which the addition or reduction of energy consuption is applied within SAP software. The specification for this reference syste is below: Space heating is provided by the defined Solar Assisted Heat Pup using perforance data recorded in the Product Characteristics Database (PCDB). Water heating is provided by a 160 litre cylinder with integral electric iersion and a anufacturer s declared heat loss of 2.21 kwh/day (when cylinder is 45K above the test laboratory air teperature). The cylinder is installed outside the heated space. No solar water heating syste In SAP 2009, the heat loss fro an ordinary hot water cylinder is an annual calculation defined as: Nuber of days in a year x daily heat loss for a cylinder with a standard 45K above its surrounding x teperature factor. The teperature factor (e.g. 0.6) accounts for the cylinder, when installed in the dwelling, being at a lower teperature than the standard test criteria. The above SAP assuptions are invalid for the theral store of a Solar Assisted Heat Pup, since being installed outside and partially suberged underground its heat losses will vary onthly. The theral store heat loss calculations are aended to onthly calculations and account for operation within all operating odes - see section 3.1.1. These calculations are undertaken within a separate suppleentary calculation procedure (Appendix workbook). Heat losses for the external pipework connected to the theral store for both space heating and hot water systes are also accounted for by the onthly calculation in section 3.1.1. These calculations are also undertaken within a separate suppleentary calculation procedure (Appendix workbook). Page 4 of 17
The low teperature store is not used in ode 1 and therefore excluded fro the Mode 1 calculation procedure. 2.1.1 SAP 2009 - Solar water heating calculations The contribution of captured solar energy towards hot water heating is calculated in accordance with SAP 2009 Appendix H, extract below: The solar contribution to doestic hot water is given by: s = S Zpanel Aap 0 UF f1 f2 Where: s = solar input, kwh/year S = total solar radiation on collector, kwh/²/year Zpanel = overshading factor for the solar panel Aap = aperture area of collector, ² 0 = zero-loss collector efficiency UF = utilisation factor a1 = linear heat loss coefficient of collector, W/²K f1 = collector perforance factor = 0.97-0.0367 (a1/ 0) + 0.0006 (a1/ 0)² if a1/ 0 < 20 = 0.693 0.0108 a1/ 0 if a1/ 0 20 Veff = effective solar volue, litres Vd = daily hot water deand, litres f2 = solar storage volue factor = 1.0 + 0.2 ln(veff/vd) subject to f(veff/vd) <= 1.0 Note. The overall perforance of solar water systes depends on how the hot water syste is used, e.g. daily draw-off patterns and the use of other water heating devices such as a boiler or an iersion. The procedure described here is not suitable for detailed design in a particular case. It is intended to give a representative value of the solar contribution to doestic water heating over a range of users. Insolation is deterined fro tables that account for the solar collector angle of tilt and orientation. The zero heat loss collector efficiency and linear heat loss factor are tested according to EN12975-2 (Theral solar systes and coponents - Solar collectors - Part 2: Test ethods) The solar collector perforance factor is a function of the collector s heat loss and zero heat loss efficiency. The solar storage volue factor is calculated fro the ratio of the volue of solar store and the daily water usage. When the solar storage volue is greater than the daily hot-water usage the factor is 1. The utilisation factor accounts for the agnitude of captured solar energy copared to the energy required to heat the hot water. That is, high levels of captured solar energy cannot always be utilised. 2.1.2 Application for Solar Assisted Heat Pup Systes The captured solar energy is only applicable to Mode 1 operation for the calculation procedure. Therefore, the SAP Appendix H variable (S) total solar radiation on collector is ultiplied by the fraction of incident solar energy in ode 1 (see Table 2, Section 3.1.2). In SAP the heat losses fro a solar hot water cylinder are not explicitly odelled and are therefore excluded fro the calculation of the utilisation factor. Page 5 of 17
The heat loss fro the Solar Assisted Heat Pup syste theral store and distribution pipework is substantially higher than typical losses fro solar theral systes and is therefore included in the suppleentary procedure. These losses should strictly also be included in the solar utilisation factor calculation. However, including this would introduce a coplex iterative process. To avoid the requireent for an iterative process, the usefulness of solar energy is liited to the hot water energy requireent plus the theral store and distribution pipe heat loss. The solar collector perforance factor (f1) and solar storage volue factor calculations (f2) are unchanged. 2.2 Mode 2, 3 and 4 The operating odes 2, 3 and 4 are analysed within SAP software utilising the heat pup data record held within the Product Characteristics Database (PCDB). The data foring the record is calculated according to EN15316 using laboratory easureents 1 and hourly cliate data. EN15316 deterines the Seasonal Perforance Factor (SPF) and any suppleentary heating required as a function of the plant size ratio. Hourly weather data containing air teperatures and direct and diffuse horizontal insolation were sourced fro a standard reference cliate year for Leeds 2. It is coposed of typical onthly data selected fro ten years of data. The EN15316 calculation procedure only accounts for solar energy input during cold and bright periods (Mode 2). Hourly weather data was used to calculate the onthly fraction of captured solar energy during cold periods (see table 2), when direct and diffuse insolation was greater than 10W/ 2 and cold was defined as 15ºC or lower. The fraction of captured solar energy during cold periods is ultiplied by the onthly insolation values within Appendix H of SAP 2009 and transferred to the EN15316 calculation procedure. Specified insolation values are for a south facing panel with little or no over shading. The sensitivity of heat pup Seasonal Perforance Factor to inor variations in solar collector area, orientation and tilt was found to be insignificant when assessed by the EN15316 calculation procedure, particularly given the large area of solar collector. For exaple, a tolerance of 19-25 ² is therefore peritted for a noinal tested area of 20.11 ². Additionally, hydraulically separated ultiples of collector areas are peritted in order to increase the effective heat pup output, whilst siultaneously capturing ore solar energy. In this exaple, the noinal defined collector area sizes are therefore: a) 19 to 25² b) 38 to 50² c) 57 to 75² Note: It is critical that collector areas are hydraulically separated fro any additional areas, in this exaple 19-25², since this calculation ethod assues the solar collectors will not stall. 1 See: SAP 2009 Calculation Methodology for electrically driven heat pups 2 The test reference year is coposed of onthly data fro different years (e.g. January fro year x, February fro x-3, March fro year x+5) that were considered as a typical onth fro the years available and is priarily designed for coplex dynaic building coputer odels, see Ref 1 Page 6 of 17
3 Procedure The following are the required data ites for each Solar Assisted Heat Pup syste to be recognised within SAP 2009 3 : a) Manufacturer b) Brand c) Model Nae d) Model ualifier e) Theral store volue f) The heat loss of theral store above ground at a standardised 45K teperature difference to abient external environent. Based on easureents or independent third-party siulation. g) The heat loss of theral store below ground at a standardised 45K teperature difference to surrounding ground environent. Based on easureents or independent third-party siulation. h) The heat loss for the pipes connecting the theral store to the dwelling at a standardised 45K teperature difference to abient external environent. This is calculated using typical installation pipe lengths, diaeter and insulation levels agreed with the anufacturer. i) Solar collector heat loss W/ 2 /K fro UKAS or equivalent third party test easureents to EN12975-2:2006 j) Solar collector efficiency at zero heat loss fro UKAS or equivalent third party test easureents to EN12975-2:2006 k) Area of solar collector ( 2 ) l) Solar collector pup power (Watts) The user selects the collector brand and odel and enters the details of the dwelling and heating syste into the suppleentary calculation (Appendix ) workbook. The user ust also enter the following paraeters into SAP calculation software: a) Space heating provided by the recognised Solar Assisted Heat Pup Syste fro the Product Characteristics Database (PCDB) record according to brand, odel and odel qualifier. b) Water heating is provided by a 160 litre cylinder with integral electric iersion and a anufacturer s declared heat loss of 2.21 kwh/day. c) The hot water cylinder is specified as outside the heated space. The calculation procedure calculates the decrease or increase in energy consuption relative to the above scenario as detailed in section 3.1. 3.1 Calculations The calculation procedure deterines the difference in energy required for hot water heating between that required by the Solar Assisted Heat Pup Syste and that required by the reference syste (see Section 2.1 for details). This is undertaken in the following sequence: 1. The energy required for hot water heating for the Solar Assisted Heat Pup Syste is calculated in accordance with sections 3.1.1 to 3.1.5. 2. The energy consuption for the reference syste is calculated in accordance with section 3.1.6. 3 Paraeters (e) (l) are recorded within the Appendix workbook (suppleentary calculation procedure), whilst all others are recorded within the workbook and the Product Characteristics Database (PCDB). Page 7 of 17
3. The overall energy perforance of the Solar Assisted Heat Pup is copared to the reference syste and is calculated in accordance with section 3.1.7. 3.1.1 Theral store heat losses and distribution pipe losses For each onth calculate the heat loss fro the theral store according to (1). store, ( T T ) ( T T ) air,45 K store, air, grd,45 K store, ground, Nd (1) 45 where: Nd is the nuber of days in the onth. air,45k and grd,45k are the daily heat losses for the section of theral store above and below ground respectively, standardised to a 45K teperature rise above its surroundings. These are supplied by the anufacturer either fro physical tests or fro a siulation conducted by an independent third-party. Tstore is the onthly average teperature of the theral store (i.e. the anufacturer s defined set point teperature). T is the onthly air teperature used in SAP 2009 air, Tground, is the onthly ground teperature set to the average yearly air teperature for each onth Note: In ode 1 the teperature of the theral store will be higher than the set-point (defined by anufacturer) due to the captured solar energy heating the theral store directly and thereby increasing its standing heat loss above that calculated in (1). The beneficial captured solar gains are liited to the axiu hot water energy required plus the theral store heat loss and distribution pipe heat loss, instead of using the solar utilisation factor as explained in part 3.3.3. Therefore, if a higher standing heat loss than that at the defined set-point were calculated, it would erely increase solar energy contribution by the sae aount, with no net change in the overall energy consuption. For each onth calculate the heat loss connecting the external theral store to the hot water heating and spacing heating distribution systes: pp, pp, air,45 K ( Tstore, Tair, ) pp, grd,45 K ( Tstore, Tground, ) Nd (2) 45 where: pp, air and pp, grd is the pipe heat loss to air and ground standardised to a 45K teperature rise above its surroundings. Standardised pipe heat losses agreed with the anufacturer are held within the suppleentary calculation (Appendix ) workbook. A sall range of options are assigned based on typical pipe diaeters, lengths and insulation levels between the theral store and the dwelling. These options account for heat losses during space heating and hot water heating operation with four installation options provided in the table below. Page 8 of 17
Pipe exposure and insulation 2.5 or less of insulated pipe, ostly above ground 2.5 or less of insulated pipe, ostly buried More than 2.5 but less than 5 of insulated pipe, ostly buried More than 2.5 but less than 5 of insulated pipe, ostly above ground Table 1 - Pipe heat loss data required Standardised heat loss kwh/day Air Ground - x.xx x.xx - - x.xx x.xx - The heat losses in Table 1 ust use the following specifications: 1. 2.5 or 5 refers to a single pipe length (e.g. the flow or return), but the total heat loss is doubled in the suppleentary calculation (Appendix ) workbook to account for both. 2. Standardised refers to a teperature difference of 45K between the pipe and the surrounding environent. 3. Pipe inside diaeter is X with insulation thickness of X of theral conductivity (λ value) of X W/K. The values denoted as X are defined by the anufacturer during the SAP Product Recognition stage and recorded in the suppleentary calculation (Appendix ) workbook. 4. The insulated pipe conduction heat loss (i.e. excluding the heat surface coefficient is calculated fro: 2 l ln( r2 / r1), where l is the total pipe length (5 or 10) and r and 2 r 1 is the inside and outside radius of the insulated pipe. 5. A 0.13 ²K/W surface heat transfer resistance is applied to the insulated external pipe surface area above ground, whilst no surface resistance is applied to the pipe installed below ground. 6. The heat loss to the air over a 24 hour period (kwh) for a teperature difference of 45K between the pipe and the surrounding environent is: pp, air 45 0.024 1 0.13 2 l ln( r / r) 2 rl 2 1 2 7. The heat loss to the ground over a 24 hour period (kwh) for a teperature difference of 45K between the pipe and the surrounding environent is: 45 0.024 2 l ln( r / r) pp, grd 2 1 3.1.2 Solar water heating contribution Calculate the onthly solar heating contribution to water heating as: f N H Z A f( a / ) (3) S, s d s panel ap 0 1 0 Page 9 of 17
s is the incident annual radiation on collector, kwh/²/year (see Table H2, SAP 2009) f is the onthly to annual ratio (Table H3, SAP 2009) N d is the nuber of days in the onth H s is the onthly fraction for war and sunny days (see Table 2 below) Z is the over shading factor for the solar collector panel A ap is the aperture area of collector, ² 0 is the zero-loss collector efficiency a 1 is the linear heat loss coefficient of collector, W/²K f( a / ) is collector perforance factor defined as: 1 0 f( a / ) 0.97 0.0367 a / 0.0006 a / ² if a / < 20 1 0 1 0 1 0 1 0 f( a / ) 0.693 0.0108 a / if a / 20 1 0 1 0 1 0 Liit the onthly solar contribution to: xs, store, hw, where: (4) hw, is the onthly hot water deand ([45 ] in SAP 2009 Worksheet). store, is the onthly heat loss fro the store calculated fro equation (1) Note: Since the theral store s heat loss can be recouped by the solar contribution (for Mode 1), in theory the utilisation factor should include the large theral store and distribution pipe heat losses. However, introducing the heat losses into the solar utilisation factor calculation would ean introducing an iterative calculation which is not practical in SAP. Instead, the usefulness of the captured solar energy is liited to the hot water energy requireent plus the theral store s associated standing heat loss (i.e. the theral store and distribution pipework heat losses). This approach is reasonable given that the SAP solar utilisation factor approach was devised for noral sized solar water heating syste and Solar Assisted Heat Pup Systes have very large theral stores and solar collector areas. Page 10 of 17
Captured solar energy fraction delivered to theral store H s Captured solar energy fraction delivered to low teperature theral store January 0.0% 98.4% February 0.0% 99.3% March 5.4% 94.4% April 8.2% 91.6% May 41.1% 58.8% June 46.6% 53.3% July 85.1% 14.7% August 77.0% 22.9% Septeber 56.7% 43.1% October 7.8% 91.7% Noveber 1.5% 97.3% Deceber 2.3% 94.7% Table 2 - Fraction of captured solar energy delivered to theral store and low teperature theral store The daily captured solar energy delivered to the theral store is the fraction delivered in daylight hours when the air teperature exceeds 15ºC and the horizontal direct and diffuse insolation is greater than 10W/ 2. 3.1.3 Hot water uplift The theral store is heated by the heat pup to a teperature set point defined by the anufacturer (i.e. 38ºC). On war and sunny days captured solar energy will increase the teperature further. However, the teperature of the theral store ay not be sufficient to satisfy the required doestic hot water teperature, even during war and sunny periods. The noinal average hot water delivery teperature in SAP 2009 is approxiately 52ºC but varies onthly. A direct electric inline heater is provided to suppleent hot water heating and its operation is analysed within the Appendix procedure. This is calculated as the difference (shortfall) between the axiu delivery teperature delivered by the theral store and the SAP onthly hot water teperature. This section estiates any shortfall in the water heating that is et by the electric inline heater and is the aount of energy required to heat hot water to the desired teperature (e.g. 52ºC 4 ) above the theral store teperature. First, the onthly theral store teperature rise due to solar heat gains is estiated fro the energy balance and the heat capacity of the theral store (i.e. the volue ultiplied by the specific heat capacity of water). This is the net heat gain resulting fro the teperature rise due to the solar water heating contribution, less any theral store and distribution pipe heat losses, divided by the heat capacity. This will give the accuulated teperature rise at the end of the onth. Dividing by the nuber of days in the onth will give the expected average teperature rise at the end of each day. The theral store teperature will accuulate each day, which will increase the theral store s heat losses, until such tie as the heat losses equal the captured solar energy. 4 In SAP 2009 the teperature of the delivered hot water varies onthly and is calculated by adding the onthly values of SAP Table 1d and SAP Table G2. Page 11 of 17
Calculate the average daily teperature rise due to solar heat gains for each onth thus: T [( )] 3600 / (4.19 V N ) (5) st, s. hw. st, pp, hs d S, is the onthly solar heating contribution calculated in (3) hw, is the onthly energy delivered to the doestic hot water (SAP box 45 + 46) st, is the onthly heat loss fro the theral store at the required onthly hot water supply teperature ( T hwd, ). This is calculated by substituting Thwd, in place of Tstore, in equation 1. is the priary pipe heat loss assuing the theral store teperature pp, T and is estiated fro equation (2) by replacing T, is hwd, T hwd,. store with V hs is the volue of the theral store N d is the nuber of days per onth 4.19 is the specific heat capacity of water in kj/litres/k 3600 is a ultiplier that converts fro kwh to kj Deterine the fraction of days per onth (P in(iso),) ), when considered in isolation, where the suppleentary electric inline heater is required to raise the hot water teperature (fro heat supplied by the theral store at the defined teperature set point) to the desired hot water teperature according to (6): If, > 0 p Tst in( iso), ( T T ) If, = 0 then p ( ), 1 Tst in iso hwd, store Nd Tst, (6) If the result of (6) is greater than 1 reset to 1. T store, is the teperature the theral store reaches fro use of the heat pup alone (i.e. the set-point teperature, defined by Manufacturer) T hwd, is the average teperature of the delivered hot water teperature which varies onthly (su of SAP Table 1d and SAP table G2). Equation (6) considers onths in isolation and not consecutively. When considered consecutively the theral store ay have reached the required hot water teperature in the previous onth (i.e. the suer onths when operating in Mode 1, where the set-point teperature T store, ay be exceeded) and would reain so until the required energy for hot water services exceeds the captured solar energy Page 12 of 17
(less heat losses). To deterine the fraction of days per onth, when considering the onths consecutively, the results of equation (6) are applied to each onth as noted below: a) In calendar order, note the first onth where the fraction of days (where suppleentary hot water heating is required) is less than 1. b) In reverse calendar order, starting fro Deceber note the first onth where the fraction of days is less than 1. c) For the onths between (a) and (b), but not onths (a) or (b), set the fraction of days to zero. The fractions of days for all other onths are unaltered. The fraction of days per onth where suppleentary hot water heating is required when considered consecutively is p in,. Calculate the suppleentary energy required for each onth, if any, by the electric inline heater: up, p ( T T ) in, hw, hwd, store [ ] [1 CoP.. hw] ( Thwd, Tcold, ) (7) hw, is the onthly energy delivered in the hot water (SAP box 45 + 46) CoP.. hw is the heat pup coefficient of perforance when delivering heat fro the low teperature theral store to the theral store. 3.1.4 Circulator energy consuption Calculate the annual electricity consuption of the circulation pup during ode 1 as: circ h circulator power(w) /1000 (8) h = 1248hrs, which is the nuber of hours per year that the syste operates in Mode 1. This is defined as the nuber of hours where the air teperature exceeds 15 ºC and the direct and diffuse insolation exceeds 10 W/ 2. 3.1.5 Su the individual contributions Using the results of (1) to (8) calculate the annual water heating energy as below, where siga refers to the onthly suation over the year. 12 [( ) / CoP.. ] (9) hw, syste circ uplift, pp, store, hw. s, hw 1 The CoP.. hw is taken to be the sae value calculated in EN15316 for space heating operation. This is a reasonable assuption since it represents the Coefficient of Perforance (CoP) of heat delivery to the theral store, which provides both space heating and hot water heating services. Page 13 of 17
3.1.6 Water heating consuption of the reference syste The energy consuption of the reference syste is calculated using SAP conventions within SAP software. The reference hot water syste is an electric iersion within a 160 litre tank installed outside the heated space. The tank has a anufacturer s declared heat loss of 2.21 kwh/day. 12 [( 0.6 N ) ] (8) hw, ref refstore, d d hw, 1 where: refstore, d is standardised daily heat loss of 2.21 kwh/day 0.6 is the teperature factor (See table 2b of SAP 2009) N d is the nuber of days per onth hw, is the onthly energy delivered in the hot water (boxes (45) of SAP worksheet) 3.1.7 Overall energy savings The overall energy savings (or penalty) calculated by the suppleentary calculation (Appendix ) workbook is: Energy saving (or penalty if negative) = hw, ref hw, syste (9) Page 14 of 17
4 References 1. Standard reference year weather data for Leeds fro CIBSE Guide J: Weather, Solar and Illuinance Data. 2. The Governent s Standard Assessent Procedure for Energy Rating of Dwellings 2009 edition incorporating RdSAP 2009, March 2010, BRE Page 15 of 17
Appendix This appendix lists the hours of operation of ode (Table A1) and the table data used in the EN15316 calculation procedure (Table A2 and A3). Mode 1 Hours when air teperature exceeds 15ºC and direct and diffuse insolation exceeds 10W/ 2 Mode 2 Hours when air teperature is 15ºC or below and direct and diffuse insolation exceeds 10W/ 2 Mode 3 Hours of daylight when air teperature is 15ºC or below and direct and diffuse insolation is 10W/ 2 or below Mode 4 Hours of darkness or when not in Mode 1, Mode 2 or Mode 3. Mode 1 Mode 2 Mode 3 Mode 4 hours hours hours hours January 0 226 32 486 February 0 256 30 386 March 12 339 3 390 April 30 374 4 312 May 137 338 9 260 June 194 286 30 210 July 373 116 38 217 August 291 149 25 279 Septeber 188 175 27 330 October 16 290 38 400 Noveber 3 235 34 448 Deceber 4 186 31 523 Table A1 - Hours operation by ode Solar energy transitted In kwh per onth Mode 2 January 221.11 February 362.96 March 557.47 April 740.04 May 596.16 June 555.89 July 153.27 August 204.01 Septeber 289.25 October 435.62 Noveber 259.87 Deceber 176.40 Table A2 - Solar energy transitted to collector for EN15316 calculations Page 16 of 17
Note - Table A2 uses the following assuptions: Solar collector easured efficiency at zero heat loss of 73% Solar collector heat loss coefficient of 15.11 W/ 2 /K Solar collector on 30º slope and south facing Solar collector area = 20.11 ² Over shading = none Mode 2 Cold and bright Mode 3 Cold and dull during the day Mode 4 Night tie Low teperature theral store teperature ºC (sae as outside) Low teperature theral store teperature ºC (sae as outside) Low teperature theral store teperature ºC (-5K below outside) January 5.1 5.4-1.1 February 6.1 6.7-0.1 March 7.3 2.5 1.0 April 8.9 8.4 2.7 May 10.1 11.9 4.8 June 12.3 15.1 7.5 July 13.0 17.8 10.6 August 13.2 15.5 9.2 Septeber 12.2 14.9 7.2 October 10.8 11.3 4.7 Noveber 7.7 8.2 1.8 Deceber 6.7 7.6 1.2 Table A3 Low teperature theral store teperature for Mode 2, 3 and 4. Page 17 of 17