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- Andrén, Lars, et al.
(author)
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Handbok för kombinerade sol- och biovärmesystem : Teknik - System - Ekonomi
- 2012
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Reports (other academic/artistic)abstract
- Handboken beskriver olika solfångarkonstruktioner och solvärmekretsens ingående komponenter och ger en grundlig inblick i ackumulatortankens konstruktion och funktion. I boken finns förslag på systemutformning, olika tekniska lösningar och hur systemen bör styras och regleras. Handboken beskriver i första hand utformning-lösning-styrning av kombinationen sol- och pelletsvärme, men tar även upp solvärme i kombination med vedpannor, värmedrivna vitvaror och värmepumpar. Värmesystem med vattenburen värme är utmärkta att kombinera med solvärme, men det är i de flesta fall enklare att få till bra lösningar vid nyinstallation, än vid komplettering av befintlig anläggning. När solvärme och pelletsvärme ska kombineras finns det många alternativ till systemutformning. Det är viktigt att vattenburna pelletssystem utformas korrekt och kombineras på rätt sätt med solvärme för att komforten ska bli hög och elanvändningen låg. Vattenmantlade pelletskaminer med ett vattenburet värmesystem är extra intressant i kombination med solvärme. När eldningen upphör i samband med att värmebehovet avtar kan solvärmen ta över. En generell slutsats är att konventionella svenska pelletspannor med inbyggd varmvattenberedning inte är lämpliga i kombination med solvärmesystem. Den typen av bränslepannor ger komplicerade systemlösningar, höga värmeförluster och det är svårt att åstadkomma en tillräckligt bra temperaturskiktning i ackumulatortanken om varmvattenberedning sker i pannan. Solvärme för varmvattenberedning kan vara ett enkelt och bra komplement till pelletskaminer som genererar varmluft. För solvärmesystem är det viktigt att kraftig temperaturskiktning erhålls när värmelagret laddas ur. Det betyder att ackumulatortankens (eller varmvattenberedarens) nedre vattenvolym ska kylas ner till temperaturer som ligger nära ingående kallvattentemperatur. Ackumulatortankens mellersta del bör kylas till samma temperatur som radiatorreturen. Vid design av solfångarkretsen måste överhettning och stagnation kunna klaras utan risk för glykolnedbrytning eller andra skador på värmebärare eller rörkrets (och andra komponenter i kretsen). Partiell förångning minskar risken för att glykolen skadas då solfångaren når höga stagnationstemperaturer. Solfångarens glykolblandning tillåts koka (förångas) på ett kontrollerat sätt så att endast ånga blir kvar i solfångaren. Vätskevolymen i solfångaren samlas upp i ett större expansionskärl och systemet återfylls när vätskan kondenserar. Dränerande solfångarsystem med enbart vatten är ett möjligt alternativ till konventionella solfångare. De kräver en större noggrannhet vid installationen, så att sönderfrysning undviks. Dränerande systemlösningar är relativt ovanliga i Sverige. Om solfångaren under senhöst-vinter-tidig vår kan arbeta med att förvärma kallvatten från 10 till 20 ºC erhålls en betydligt bättre verkningsgrad på solfångaren (och framför allt ökar värmeutbytet då drifttimmarna ökar väsentligt) än om radiatorreturen (som i bästa fall ligger på temperaturnivån 30 - 40 ºC) ska förvärmas. Därför bör radiatorreturen placeras en bra bit upp från botten i ackumulatortanken och tappvarmvattnet ska förvärmas i en slinga som börjar i tankens botten. Om det finns ett VVC-system måste systemet anslutas på ett speciellt sätt så att ackumulatortankens temperaturskiktning inte störs. En viktig parameter vid ackumulatortankens utformning är att värmeförlusterna hålls låga. Det är viktigt för att klara tappvarmvattenlasten med solvärme under mulna perioder sommartid (men också för att hålla energianvändningen låg). I moderna hus, där ackumulatortanken i regel placeras i bostaden, blir det en komfortfråga att undvika övertemperaturer i det rum där värmelagret placeras. En bra standard på isoleringen (med minimerade värmeförluster) kräver att det finns ett lufttätt skikt över hela isoleringen som dessutom sluter tätt mot röranslutningar. Ofrivillig självcirkulation i anslutande kretsar som kan kyla av och blanda om ackumulatortankens vattenvolym, bör förhindras med backventiler och nedböjning av rören i isolerskiktet eller direkt utanför tanken.
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| 2. |
- Bales, Chris, et al.
(author)
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External DHW units for solar combisystems
- 2003
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In: Solar energy. - 0038-092X. ; 74, s. 193-204
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Journal article (peer-reviewed)abstract
- This article compares seven different external DHW units, comprising flat plate heat exchanger and flow control, with a reference method for preparing hot water. These DHW units use different control methods. The objective of the study was to determine which methods are most effective in solar combisystems and to identify other factors that strongly influence the energy savings of the system. Five of the DHW units were judged to be of interest for the study because of their measured performance or the simplicity of their design. Of these, measurement data showed that two had the same control function although of different physical construction. Thus four DHW units were modelled in the simulation environment PRESIM/TRNSYS, parameters were identified from measured data, and annual simulations were performed with a number of parametric variations. Three of the DHW units performed significantly better than the reference system provided that they were sized correctly: microprocessor control with variable-speed pump; proportional controller with regulating valve; and a turbine pump. The most important design factors identified by the study were: the maximum possible primary flow, which needs to be suitable for the design hot water load profile; and ensuring a low temperature is returned to the store. The hot water load profile was also shown to strongly influence the energy savings, assuming that auxiliary heater's thermostat is set so that the system just meets the worst-case discharge.
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| 5. |
- Chèze, David, et al.
(author)
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Towards an harmonized whole system test method for combined renewable heating systems for houses
- 2014
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Conference paper (other academic/artistic)abstract
- The objective of this work is the development of harmonized efficiency test methods for combined renewable heating systems for houses, using a hardware-in-the-loop approach. An overview of the principles of the existing whole system test methods used by 3 research institutes involved in the project (MacSheep 2012) is given. Main objectives are realistic dynamic test sequence elaboration for solar and heat pump systems and comparison of results from tests achieved in different institutes. In order to reach these objectives, the first phase of the work aimed to harmonize the boundary conditions that comprise both the physical boundaries of the tested system as well as the climate and heat load definition, and this is presented in the first part of the article. The second part presents two methodologies to elaborate 12-days and 6-days whole system test sequences, validation results for solar and air source heat pump systems (SHP) and a methodology for achieving equal amount of space heat supplied by the tested system while at the same time providing a realistic response of the heat distribution system.
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| 7. |
- Dalenbäck, Jan-Olov, et al.
(author)
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Wood pellet and solar heating system development in Sweden. Initial result from system bench-marking test developments
- 2011
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In: ESTEC 2011 -5th European Solar Thermal Energy Conference. - Marseille, France.
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Conference paper (other academic/artistic)abstract
- Svensk Solenergi (Solar Energy Ass. of Sweden) and PellSam (Swedish Pellet Equipment Manufacturers Ass.) have joined forces to develop combined wood pellet and solar heating systems for the Nordic conditions. The cooperation has three main elements. A co-ordinated development project related to systems for single family houses (with co-financing from the Swedish Energy Agency), a common marketing campaign called “100%” (renewable heat) and certification of installers. The paper will focus on the development project. The development project comprises the development of a system design handbook and a combined system bench-marking and test method development. The test method (based on the Combitest method), is called Direct Characterization (DC) and the result is supposed to describe the annual system performance. It comprises laboratory measurements during 6 days on a whole system including (real) pellet boiler (or furnace), storage tank, controls and (simulated) solar collectors and load (based on selected weather data). The present set-up is for a typical single family building with 13 MWh space heating and 3 MWh DHW load. The test development has comprised a test of a reference boiler and 6 sample systems. Although all tested systems required less pellets than the reference boiler for the given load, only a few of the system designs take all aspects given in the handbook into account. The performance of the different systems varied a lot, from low 19 to high 37% less pellets than the reference boiler. The system tests have been carried out in two laboratories and one system has been tested in both laboratories with a reasonable agreement regarding the main parameters. The overall conclusion is that the test method seems to be possible to develop into a useful bench-mark method and that there are large possibilities for basic system improvements. Most of the tested systems consist of standard components combined into a system with a common control. Major system improvements are thus related to smaller boilers (furnaces) matched with improved and better insulated storage tanks (allowing reduced collector area) and better system controls (e.g. allowing less start and stop of the boiler/furnace). It is thus the intention to carry out a second round of system tests to include improved systems.
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| 8. |
- Fiedler, Frank, et al.
(author)
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Annual CO-emissions of combined pellet and solar heating systems
- 2007
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In: ISES Solar World Congress 2007, ISES 2007. ; , s. 2468-2472
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Conference paper (other academic/artistic)abstract
- Emissions are an important aspect of a pellet heating system. High carbon monoxide emissions are often caused by unnecessary cycling of the burner when the burner is operated below the lowest combustion power. Combining pellet heating systems with a solar heating system can significantly reduce cycling of the pellet heater and avoid the inefficient summer operation of the pellet heater. The aim of this paper was to study CO-emissions of the different types of systems and to compare the yearly CO-emissions obtained from simulations with the yearly CO-emissions calculated based on the values that are obtained by the standard test methods. The results showed that the yearly CO-emissions obtained from the simulations are significant higher than the yearly CO-emissions calculated based on the standard test methods. It is also shown that for the studied systems the average emissions under these realistic annual conditions were greater than the limit values of two Eco-labels. Furthermore it could be seen that is possible to almost halve the CO-emission if the pellet heater is combined with a solar heating system.
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| 9. |
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| 10. |
- Fiedler, Frank, et al.
(author)
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Carbon monoxide emissions of combined pellet and solar heating systems
- 2009
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In: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 86:2, s. 135-143
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Journal article (peer-reviewed)abstract
- Emissions are an important aspect of a pellet heating system. Low harmful emissions, particularly carbon monoxide, are a measure of a well performing system. High carbon monoxide emissions are often caused by unnecessary cycling of the burner and when the average load is below the lowest possible combustion power of the burner. Combining pellet heaters with a solar heating system can significantly reduce cycling of the pellet heater and avoid the inefficient summer operation of the pellet heater. Five combined systems representing the range of typical solutions of this system type and one recently developed system have been studied, modelled and simulated. These systems are compared to a reference system, which is based on a pellet boiler and is not combined with a solar heating system. The aim was to study CO-emissions of the different types of systems and to analyse the potential of CO-emission reduction when the pellet heater is combined with a solar heating systems. Another aim was to compare the yearly CO-emissions obtained from simulations under realistic dynamic conditions with the yearly CO-emissions calculated based on the values that are obtained by the standard test methods. The study was performed with the simulation tool TRNSYS. The parameter used in the study have been identified from lab measurements on existing pellet boilers/stoves and solar heating systems. The results from the simulations show that it is possible to almost halve the CO-emission if the pellet heater is combined with a solar heating system. The results also show that the CO-emission of existing combined solar and pellet heating systems can be drastically reduced if the pellet heater is properly controlled and some basic design rules are observed. This can also be seen when analyzing the results for the new system concept where these rules have been taken into account. Comparing the yearly CO-emissions obtained from the simulations with the yearly CO-emissions calculated based on the standard test methods shows that using the latter give too low CO-values for the whole year. It is also shown that for the existing systems the average emissions under these realistic annual conditions were greater than the limit values of two Eco-labels.
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