Abstract

Sweden has the goal of reaching a fossil independent transportation sector by 2030. Two ways to reach the goal is to increase the use of electric vehicles or produce more biofuels. Both alternatives could be powered by forest residue, which is an underutilized resource in the country. Electricity could be produced in a biomass fired Combined Heat and Power (CHP) plant, and biofuel could be produced in a biorefinery through gasification of biomass and Fischer-Tropsch process. When located in Stockholm County, both system can also distribute heat to the district heating system. It is however important to use the biomass in an energy-efficient way. The scope of this work has been to analyze the efficiency together with environmental and economic aspects of the two systems.  To assess the efficiency and environmental impact of the two systems a forest to wheel study was made of the systems where the product was studied from harvesting of forest residue to driving the vehicle. The studied functional units were: kilometers driven by vehicle, kWh of district heating, CO2-equivalents of greenhouse gases and MWh of forest residue. The system using CHP technology and electric vehicles outperformed the biorefinery system on the two first functional units. Using the same amount of forest residue more than twice as much district heating and almost twice as many driven kilometers were produced in this system. The study also showed that both systems avoids significant greenhouse gas emissions and can be part of the solution to decrease emissions from road transportation.  The profitability of investing in a CHP plant or a biorefinery was calculated through the net present value method. It showed that the expected energy prices are too low for the investments to be profitable. The CHP plant investment has a net present value of -1.6 billion SEK and the biorefinery investment has a net present value of -4.6 billion SEK. Furthermore, the biorefinery investment entails higher risk due to the high investment cost and uncommercialized technology. Both systems face barriers for implementation, these barriers have been studied qualitatively.  Sverige har som mål att skapa en fossiloberoende fordonsflotta till år 2030. Två vägar som pekats ut för att nå målet är att öka användningen av eldrivna fordon eller att producera mer biobränsle. Båda alternativen kan drivas av skogsavfall, en råvara som det finns gott om i Sverige. Elektricitet kan produceras av skogsavfallet i ett kraftvärmeverk, och biobränsle i ett bioraffinaderi genom användning av förgasning och Fischer-Tropschmetoden. I Stockholms län skulle båda systemen dessutom kunna producera värme till Stockholms fjärrvärmesystem. Det är dock viktigt att använda skogsavfallet på ett resurseffektivt sätt. Därför undersöker detta arbete effektiviteten av de två olika systemen tillsammans med en analys av växthusgasutsläpp och ekonomiska förutsättningar.  För att kunna utvärdera effektiviteten och klimatpåverkan av de två olika systemen utfördes en ”skog-till-hjul”-analys där produkten undersöktes från ursprunget, till drivandet av ett fordon. För att utföra studien definierades fyra funktionella enheter. De funktionella enheterna var: körsträcka med bil mätt i kilometer, kWh fjärrvärmeproduktion, CO2 ekvivalenter av växthusgasutsläpp och MWh skogsavfall. Studien visade att systemet där skogsavfallet används i ett kraftvärmeverk för att producera elektricitet och ladda elbilar hade bättre resultat i de två första funktionella enheterna. Systemet producerade nästan dubbelt så lång körsträcka och mer än dubbelt så mycket fjärrvärme som systemet där skogsavfallet används i ett bioraffinaderi och biobränslet används i dieselbilar. Studien visade även att båda system kan bidra till att sänka växthusgasutsläppen från transportsektorn.  Lönsamheten att investera i ett kraftvärmeverk eller bioraffinaderi beräknades med nuvärdesmetoden. Studien visade att de förväntade framtida energipriserna är för låga för att investeringarna ska bli lönsamma. Kraftvärmeanläggningen hade ett nuvärde på -1.6 miljarder kronor, och bioraffinaderiet ett nuvärde på -4.6 miljarder kronor. Dessutom ansågs investeringen i ett bioraffinaderi vara en hög risk på grund av den höga investeringskostnaden och att tekniken idag inte är kommersialiserad. Det finns även en rad andra barriär för att genomföra de två olika systemen, dessa barriärer har studerats kvalitativt i arbetet. 

Abstract

The controlling of modern district heating systems requires accurate models and simulation tools. The description and necessary verification of a model that sets these ambitions is a matter of this contribution. The model comes out of the known method-plug flow modelling. The implemented model works on the pulling principle when the amount of heat from the producer is "pulled" by the customer. The model was implemented and verified on the date of the local operator of the heating plant and distribution network. The model has been set to the parameters of the part of a real DH network, and its accuracy has been tested about traffic delays and heat loss in the pipelines. For the present experiment, the full knowledge of the heat demand was considered. These were optimal conditions and perhaps not just because of it the result that the pull plug flow model achieved was a quite good matching the measured and calculated values. (C) 2019, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved. Technology Agency of the Czech Republic [TH02020979]

Abstract

A solar hybrid district heating network integrated with a seasonal borehole thermal energy storage is dynamically simulated and analyzed over a 5-year period. The system is devoted to satisfying the space heating and domestic hot water requirements of a small-scale district consisting of 6 typical Italian single-family houses, located in Naples, with home charging of 6 plug-in electric vehicles. Eight different plant schemes differing in terms of solar field configuration and/or back-up system used for compensating the intermittency of solar source are investigated. Two different configurations of solar field are analyzed: the first one with solar thermal collectors only and the second one integrating solar thermal collectors and photovoltaic panels coupled with a battery storage; three different alternative auxiliary units are considered: natural gas-fired boiler, natural gas-fueled internal combustion engine-based micro-cogeneration unit and wood pellet boiler. An additional operating scheme is also proposed to better exploit the solar energy for domestic hot water production. The primary energy consumption, the carbon dioxide emissions and the operating costs of the proposed plant configurations are evaluated based on simulation results and then compared with those associated to a conventional decentralized heating system in order to assess the main energy, environmental and economic benefits/drawbacks.

Abstract

Drag reducing surfactants can be applied to decrease pressure losses in closed circulation pipelines systems like district heating and cooling. This article represents empirical lab scale study of the two drag reducing products developed by AkzoNobel (Sweden) specifically for aqueous solutions for different temperature ranges. Two main issues stopped previous researches of drag reducing agents: heat transfer reduction in shell and tube heat exchanger and environmental concerns. Current shift to heat supply based on renewable energy sources and small-scale biogas CHP plants will no longer require such kind of heat exchangers. It opens opportunities for new surfactants and its application in district heating. This research outlines environmental properties of the two surfactants including its biodegradability rates.