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Karlsson, Björn
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Publications (10 of 20) Show all publications
Amiri, S., Henning, D. & Karlsson, B. (2013). Simulation and introduction of a CHP plant in a Swedish biogas system. Renewable energy, 49(SI), 242-249
Open this publication in new window or tab >>Simulation and introduction of a CHP plant in a Swedish biogas system
2013 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 49, no SI, p. 242-249Article in journal (Refereed) Published
Abstract [en]

The objectives of this study are to present a model for biogas production systems to help achieve a more cost-effective system, and to analyse the conditions for connecting combined heat and power (CHP) plants to the biogas system. The European electricity market is assumed to be fully deregulated. The relation between connection of CHP. increased electricity and heat production, electricity prices, and electricity certificate trading is investigated. A cost-minimising linear programming model (MODEST) is used. MODEST has been applied to many energy systems, but this is the first time the model has been used for biogas production. The new model, which is the main result of this work, can be used for operational optimisation and evaluating economic consequences of future changes in the biogas system. The results from the case study and sensitivity analysis show that the model is reliable and can be used for strategic planning. The results show that implementation of a biogas-based CHP plant result in an electricity power production of approximately 39 GW h annually. Reduced system costs provide a profitability of 46 MSEK/year if electricity and heat prices increase by 100% and electricity certificate prices increase by 50%. CO2 emission reductions up to 32,000 ton/year can be achieved if generated electricity displaces coal-fired condensing power.

Place, publisher, year, edition, pages
Elsevier, 2013
Keywords
Biogas system, CO2 emissions, Energy systems optimisation, Combined heat and power plant, Marginal electricity
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-85624 (URN)10.1016/j.renene.2012.01.022 (DOI)000309902000051 ()
Available from: 2012-11-26 Created: 2012-11-26 Last updated: 2017-12-07
Molin, A., Widén, J., Stridh, B. & Karlsson, B. (2010). Konsekvenser av avräkningsperiodens längd vid nettodebitering av solel. Stockholm: Elforsk AB
Open this publication in new window or tab >>Konsekvenser av avräkningsperiodens längd vid nettodebitering av solel
2010 (Swedish)Report (Other academic)
Abstract [en]

The way that owners of PV systems are handled today gives, in practice, installations of very small PV systems relative to what would be possible if all appropriately oriented roof and facade surfaces were fully exploited. This problem occurs because there is a surplus of PV electricity for the system owner, who receives a zero or low value in relation to the electricity purchases that are avoided. For single-family houses, this means that without net billing it is economically optimal to install only up to about 2-7 m2 of the approximately 60 m2 that are available on the roof of a single-family house. Other end-user types, such as multi-family buildings, agriculture and industry, also show low use of available surfaces. With the current system, the major part of the possible PV production on buildings is hindered. This electricity production does not exploit any new land and has a potential in Sweden of about 10-15 TWh, assuming that 25% of the roof and wall surfaces that have at least 70% of optimum solar radiation are exploited.

The effects of five different scenarios, without and with monthly or annual net billing for an electricity consumer who is also a PV electricity producer have been studied for ten different building types, including three single-family houses, two multi-family buildings and five other properties. The implications for four actors – the solar electricity producer, the grid owner, the electricity trader and the Swedish state – have been calculated. It is thus 200 different combinations that are reported. For each combination the outcome at any system size can also be seen in the reported figures.

The amount of saved electricity for the PV owner depends substantially on the time-horizon of the net billing period. Monthly net billing would drastically improve the utilization of roof areas, but still limits the utilization. Annual net billing gives a similar additional improvement. With annual net billing, the roofs of all the studied types of properties could be covered either entirely with solar cells or as much as needed to cover the annual needs of electricity. A net billing limit, for example 63A=43.5 kW=313 m2, would be a size delimiter for larger buildings.

Grid owners would be affected in the form of reduced revenues for the electricity transfer, reduced losses in the local grid and increased revenue from excess electricity which the PV owner donates to the grid.

For electricity traders increasing system size means that sales to the PV owner decrease in the same way as bought electricity is saved for the PV owner. The balance responsible actor (BA), which takes care of generated solar electricity, can usually make a profit due to the price profile. This could also be the grid owner, or the BA designated by the grid owner, or an electricity trader chosen by the system owner depending on how the net billing is handled. If the same electricity trader is affected by the reduction in electricity sales and earnings due to the price profile, this will be favourable for the electricity trader.

Looking at tax from PV installations, net billing has the same economic effect as if the PV owner had made an energy efficiency measure. The calculations have not taken into account the state's tax revenue of the investment, which today is higher than the loss of revenue for energy tax and VAT.

For the further development of the PV market in Sweden it is of utmost importance to make it possible, as soon as possible, for PV system owners to get a reasonable compensation for their excess electricity. Net billing would be an easy way to solve this problem. The most practical and easiest way to achieve net billing would be if the grid owner could send a net value to the electricity trader. The period for net billing should be longer than one month if all available roof and wall areas are to be optimally utilized.

Abstract [sv]

Dagens hantering av solelproducenter ger i praktiken installationer av väldigt små solelanläggningar i förhållande till vad som vore möjligt om alla lämpligt orienterade tak- och fasadytor skulle utnyttjas fullt ut. Problemet beror på att det uppstår ett solelöverskott för solelproducenten som får inget eller bara ett lågt värde i förhållande till sparad köpt el. För småhus innebär det att utan nettodebitering är det för solelproducenten ekonomiskt optimalt att endast installera upp till ca 2-7 m2 av de ca 60 m2 som finns tillgängligt på ett småhus. Även andra användartyper, som flerbostadshus, lantbruk och industri, uppvisar låg utnyttjandegrad. Med nuvarande system hindras då merparten av solelproduktionen på byggnader, som inte exploaterar någon ny mark och som har en potential i Sverige på ca 10-15 TWh antaget att 25% av de tak och fasadytor som har minst 70% av optimal solinstrålning utnyttjas.

Effekterna av fem olika scenarier, utan respektive med månads- eller årsnettodebitering för en elkonsument som även är solelproducent har studerats för tio olika hustyper, inkluderande tre villor, två flerbostadshus och fem andra fastigheter. Konsekvenserna för de fyra aktörerna solelproducent, nätägare, elhandlare och staten har beräknats. Det blir därmed 200 olika kombinationer som redovisas. För varje kombination kan dessutom utfallet vid godtycklig anläggningsstorlek utläsas i de redovisade figurerna.

Mängden sparad el för solelproducenten beror kraftigt på avräkningsperiodens längd. Månadsnettodebitering skulle drastiskt förbättra utnyttjandegraden av tillgängliga ytor, men begränsar fortfarande ytutnyttjandet. En ytterligare lika stor förbättring ger årsnettodebitering. Vid årsnettodebitering skulle de studerade hustypernas tak kunna täckas endera helt med solceller eller till så stor del som behövs för att täcka årsbehovet av el. En nettodebiteringsgräns, exempelvis 63A = 43,5 kW = 313 m2, blir en begränsning för större byggnader.

Nätägarna påverkas i form av minskade intäkter från den rörliga elöverföringsavgiften, minskade förluster i det lokala elnätet och ökade intäkter från överskottsel som solelproducenten skänker till nätet.

För elhandlaren innebär ökande systemstorlek att försäljningen till solelproducenten minskar på samma sätt som sparad köpt el ökar för solelproducenten. Den balansansvarige (BA) som får ta hand om solelproducenten kan i regel göra en profilvinst. Det skulle kunna vara nätägaren, eller av nätägaren utsedd BA eller en av solelproducenten valbar elhandlare beroende på hur nettodebiteringen hanteras. Om samma elhandlare påverkas av minskad elförsäljning och profilvinst blir detta i slutändan gynnsamt för elhandlaren.

Skattemässigt får solcellsinstallationerna vid nettodebitering samma ekonomiska effekt som om solelproducenten skulle göra en energibesparing. I beräkningarna har ingen hänsyn tagits till att statens momsintäkter vid investeringen idag är högre än förlorade intäkter för energiskatt och moms.

För den fortsatta utvecklingen av solcellsmarknaden i Sverige är det av yttersta vikt att man snarast möjliggör att solelproducenter kan få en rimlig ersättning för sin överskottsel. Nettodebitering skulle vara ett enkelt sätt att lösa detta problem. Det praktiska enklaste sättet att genomföra nettodebitering skulle vara att nätägaren skickar ett nettovärde till elhandlaren. Avräkningsperiodens längd bör vara längre än en månad om man vill kunna utnyttja alla tillgängliga takytor.

Place, publisher, year, edition, pages
Stockholm: Elforsk AB, 2010. p. 80
Series
Elforsk Rapport, ISSN 1401-5706 ; 10:93
Keywords
Solceller, Nettodebitering, Avräkning, Solel
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-63599 (URN)
Available from: 2011-01-03 Created: 2010-12-23 Last updated: 2015-04-16Bibliographically approved
Gebremedhin, A., Karlsson, B. & Bjornfot , K. (2009). Sustainable energy system - A case study from Chile. RENEWABLE ENERGY, 34(5), 1241-1244
Open this publication in new window or tab >>Sustainable energy system - A case study from Chile
2009 (English)In: RENEWABLE ENERGY, ISSN 0960-1481 , Vol. 34, no 5, p. 1241-1244Article in journal (Refereed) Published
Abstract [en]

This paper presents some of the results of a power system analysis for Chile. The two major Chilean electric systems are roughly modelled and optimized using a linear programming method with the option to integrate renewable energy sources like wind power, solar power, mini-hydropower and biomass-fired power and also "municipal waste". A total of four different scenarios are outlined: reference system, new production units, gas and coal price variations and a policy measure to encourage power production based on renewable energy. The objective of the scenarios was to illustrate under what conditions integration of the different energy sources in the existing production system is possible. The study shows that even under current conditions, mini-hydro and waste to energy plants are economically viable. Wind power might be interesting alternatives if policy instrument measures are applied. On the other hand, it is hard for the other energy sources to enter the system even when higher price levels of gas and coal are applied. The system is more sensitive to coal price increases than to gas price increases and this mainly encourages CO2 emission reduction.

Keywords
Power system, Modelling, Optimisation, Renewable energy, Policy instruments
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-17135 (URN)10.1016/j.renene.2008.10.005 (DOI)
Available from: 2009-03-07 Created: 2009-03-07 Last updated: 2009-03-07
Danestig, M., Gebremedhin, A. & Karlsson, B. (2007). Stockholm CHP potential: opportunity for CO2 reductions?. Energy Policy, 35(9), 4650-4660
Open this publication in new window or tab >>Stockholm CHP potential: opportunity for CO2 reductions?
2007 (English)In: Energy Policy, ISSN 0301-4215, E-ISSN 1873-6777, Vol. 35, no 9, p. 4650-4660 Article in journal (Refereed) Published
Abstract [en]

The potential for combined heat and power (CHP) generation in Stockholm is large and a total heat demand of about 10 TWh/year can be met in a renewed large district heating system. This model of the Stockholm district heating system shows that CHP generation can increase from 8% in 2004 to 15.5% of the total electricity generation in Sweden. Increased electricity costs in recent years have awakened an interest to invest in new electricity generation. Since renewable alternatives are favoured by green certificates, bio-fuelled CHP is most profitable at low electricity prices. Since heat demand in the district heating network sets the limit for possible electricity generation, a CHP alternative with a high electricity to heat ratio will be more profitable at when electricity prices are high. The efficient energy use in CHP has the potential to contribute to reductions in carbon dioxide emissions in Europe, when they are required and the European electricity market is working perfectly. The potential in Stockholm exceeds Sweden's undertakings under the Kyoto protocol and national reduction goals.

Place, publisher, year, edition, pages
Elsevier, 2007
Keywords
District heating, CHP, CO2
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-17211 (URN)10.1016/j.enpol.2007.03.024 (DOI)
Available from: 2009-03-11 Created: 2009-03-11 Last updated: 2017-12-13Bibliographically approved
Trygg, L., Gebremedhin, A. & Karlsson, B. G. (2006). Resource-effective systems achieved through changes in energy supply and industrial use: the Volvo Skövde case. Applied Energy, 83(8), 801-818
Open this publication in new window or tab >>Resource-effective systems achieved through changes in energy supply and industrial use: the Volvo Skövde case
2006 (English)In: Applied Energy, ISSN 0306-2619, Vol. 83, no 8, p. 801-818Article in journal (Refereed) Published
Abstract [en]

The result presented in this paper shows that the Volvo plant can decrease its electricity use by 44% by making the use of electricity more efficient and converting from oil and electricity to district heating for hot tap-water, space heating and cooling. The increased demand of district heating makes investing in a new planned CHP and cooperation between the Volvo plant and the local energy utility production cost fall by 46% at current unit electricity price and by 64% when calculating with a European unit electricity price and investment in an optimised CHP system instead of the planned plant. The study furthermore shows that the global emissions of the greenhouse gas carbon-dioxide will be reduced by 350% a year if the two energy-supply measures are taken and the electricity unit prices are at a European level.

Keywords
CHP; Co-operation; Deregulated electricity market; District heating; Electricity price; Emission trading
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-14160 (URN)10.1016/j.apenergy.2005.09.005 (DOI)
Available from: 2006-11-27 Created: 2006-11-27 Last updated: 2009-06-05
Trygg, L. & Karlsson, B. G. (2005). Industrial DSM in a deregulated European electricity market: a case study of 11 industries in Sweden. Energy Policy, 33(11), 1445-1459
Open this publication in new window or tab >>Industrial DSM in a deregulated European electricity market: a case study of 11 industries in Sweden
2005 (English)In: Energy Policy, ISSN 0301-4215, Vol. 33, no 11, p. 1445-1459Article in journal (Refereed) Published
Abstract [en]

In 2004 Sweden will become part of a common European electricity market. This implies that the price of electricity in Swedish will adapt to a higher European electricity price due to the increase in cross-border trading. Swedish plant is characterized as more electricity-intensive than plant on the European continent, and this, in combination with a higher European electricity price will lead to a precarious scenario.

This paper studies the energy use of 11 plants in the municipality of Oskarshamn in Sweden. The aim is to show how these plants can reduce their electricity use to adapt to a European level. We have found that the plants could reduce their use of electricity by 48% and their use of energy by 40%. In a European perspective, where coal-condensing power is assumed to be the marginal production that alters as the electricity demand changes, the decrease in the use of electricity in this study leads to a reduction in global emissions of carbon dioxide of 69,000 tonne a year.

Electricity generated in Sweden emits very low emissions of carbon dioxide and have thus consequently very low external cost. The freed capacity in Sweden could therefore replace electricity generated with higher external cost and as a result lower the total external cost in Europe. The emissions from the saved electricity could also be valuable within the EU emissions trading scheme, if the emissions calculation is done assuming the marginal electricity is fossil fuel based.

Keywords
Deregulated electricity market; Electricity reduction; Global emissions
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-14156 (URN)10.1016/j.enpol.2004.01.002 (DOI)
Available from: 2006-11-27 Created: 2006-11-27 Last updated: 2009-06-05
Sundberg, G. & Karlsson, B. (2000). Interaction effects in optimising a municipal energy system. Energy, 25(9), 877-891
Open this publication in new window or tab >>Interaction effects in optimising a municipal energy system
2000 (English)In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 25, no 9, p. 877-891Article in journal (Refereed) Published
Abstract [en]

A study is presented where factorial design is used to find how some selected economic and technical factors affect the profitability of an investment in a combined heat and power plant. The study is performed on a Swedish district heating system. The minimal cost for supplying the demanded heat is calculated with a developed energy system optimisation model, MODEST. The effects on the resulting parameters, such as system cost and optimal size of steam cycle, are calculated from a series of experiments performed using high and low levels of the most relevant factors. The conclusion of the study is that both the main factors and the interactions between them have to be analysed to establish an accurate ranking of the technical and economic factors. (C) 2000 Elsevier Science Ltd. All rights reserved.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-47507 (URN)10.1016/S0360-5442(00)00022-0 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
Gustafsson, S.-I., Andersson, S. & Karlsson, B. G. (1994). Factorial design for energy System Models. Energy, 19(8), 905-910
Open this publication in new window or tab >>Factorial design for energy System Models
1994 (English)In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 19, no 8, p. 905-910Article in journal (Refereed) Published
Abstract [en]

Mathematical models are extensively used in energy analysis and have increased in scope as better and faster computers have become available. With complicated systems, it is difficult to predict accurate results if doubtful input data are changed. Traditionally, sensitivity analysis with a change of one or more of the parameters is used. If the influence of a change is very small, the first result is believed to be accurate. Problems may arise when sensitivity analysis is applied to a vast amount of data. The aim of this paper is to examine whether the calculation effort can be decreased by using factorial design. Our model, called Opera (Optimal Energy Retrofit Advisory), is used to find the optimal retrofit strategy for a multi-family building. The optimal solution is characterised by the lowest possible life-cycle cost. Three parameters have been studied here: length of the optimisation period, real interest rate and existing U-value for an attic floor. The first two parameters are found to influence the life-cycle cost significantly, while the last is of minor importance for this cost. We also show that factorial analysis must be used with great care because the method does not reflect the complete situation.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-73677 (URN)10.1016/0360-5442(94)90043-4 (DOI)
Available from: 2012-01-11 Created: 2012-01-11 Last updated: 2018-03-06
Gustafsson, S.-I. & Karlsson, B. G. (1992). Heat Accumulators in CHP Networks. Energy Conversion and Management, 33(12), 1051-1061
Open this publication in new window or tab >>Heat Accumulators in CHP Networks
1992 (English)In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 33, no 12, p. 1051-1061Article in journal (Refereed) Published
Abstract [en]

In a Combined Heat and Power (CHP) network, it is sometimes optimal to install a device for storing heat from one period of time to another. Several possibilities exist. If the electricity demand is high, while at the same time the district heating load is too small to take care of the heat from the CHP plant, it could be optimal to store heat from peak periods and discharge the storage under off-peak. It might also be optimal to store heat during off-peak and use it under the district heating peak load. The storage is then used for decreasing either the district heating demand or for decreasing the electricity load used for space heating. The paper shows how a mixed integer program is developed for use in the optimization process. As a case study, the CHP system of Malmö, Sweden, is used. Further, a sensitivity analysis is elaborated in order to show how the optimal solution will vary due to changes in certain input data.

Place, publisher, year, edition, pages
Elsevier, 1992
Keywords
Heat accumulators; Heat storage; Optimization; District heating; Combined Heat and Power; Electricity production; Linear programming; Time-of-use tariffs
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-73507 (URN)10.1016/0196-8904(92)90002-E (DOI)
Available from: 2012-01-05 Created: 2012-01-05 Last updated: 2017-12-08
Gustafsson, S.-I. & Karlsson, B. G. (1991). Is space heating in offices really necessary?. Applied Energy, 38(4), 283-291
Open this publication in new window or tab >>Is space heating in offices really necessary?
1991 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 38, no 4, p. 283-291Article in journal (Refereed) Published
Abstract [en]

New office buildings in Sweden are thoroughly insulated due to the Swedish building code. This code, however, does not consider the type of activity occurring in the building. This means that the heating equipment is designed as if no activity at all is going on. In modern offices there is a lot of equipment installed which uses electricity. This electricity is converted into heat which can be utilized for heating the premises, mostly in a direct way but also by the use of exhaust-air heat-pumps or heat exchangers. This paper deals with a modern office building plus office hotel complex located in Linköping, Sweden, about 200 km south of Stockholm. The tenants deal with the design of hard- and software for computers. The lighting and computers in the building use electricity which converts into heat. In this paper, it is shown that this electricity is all that is needed during normal conditions, i.e. when people work in the building. The building is also equipped with a district-heating system, which is designed as if no activity goes on in the building, so subsequently the heating equipment is larger than it need be. In this special case, it might have been better to install an electric heating device for hot-water heating and very cold winter conditions, instead of using district heating. This is so even if district heat is about half the unit price compared with that due to the dissipation of electricity. At present, when district heating is used, no measures for saving heat can be profitable due to the low district-heating price. The fact is that the tenants complain of too much heat instead of too little: the prevailing indoor temperature was about 24° C in January 1990 even though 20° C would have been sufficient. There is subsequently a need for a properly working regulation system. The one currently in use is designed to a modern standard, but is not able to maintain temperatures at a modest level.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-73124 (URN)10.1016/0306-2619(91)90081-8 (DOI)
Available from: 2011-12-16 Created: 2011-12-16 Last updated: 2017-12-08
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