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Tämä tiekartta tiivistää Suomen Akatemian yhteydessä toimivan Strategisen tutkimuksen neuvoston rahoittaman EL-TRAN-konsortion (2015–2021) työn ilmastoneutraaliin ja resurssitehokkaaseen sähköenergiajärjestelmään siirtymiseksi. Tiekartta erottaa kolme vaihetta tässä energiasiirtymässä, jossa sähköstä tulee asteittain energiajärjestelmän perusta. Ensimmäisessä vaiheessa uusiutuvan sähkön tuotanto kasvaa voimakkaasti. Siitä muodostuu useimmissa maissa keskeisin energiaresurssi olemassa olevien ilmastoneutraalien tai vähähiilisten resurssien kuten vesivoiman, bioenergian ja ydinvoiman rinnalle. Toisessa vaiheessa lisääntynyt sääriippuvan, vaihtelevan sähköntuotannon määrä vaatii lisääntyvää varavoima- ja energiavarastokapasiteettia sekä kulutuksen joustoa myös kansainvälisten energiamarkkinoiden avulla. Näillä keinoilla hallitaan ajoittaisia ali- ja ylituotantotilanteita, ylläpidetään tuotannon ja kulutuksen välistä tasapainoa ja taataan sähköistyvän yhteiskunnan toimintakyky. Kolmannessa vaiheessa liikennesektorin, rakennusten ja teollisuuden energiankäyttö siirtyy yhä enemmän sähköön sektorikytkennän ansiosta. Energiajärjestelmää hallitaan älyverkkojen avulla. Järjestelmään kuuluu sekä pienten tuottajakuluttajien hajautettuja resursseja, kuten energiayhteisöjä ja mikroverkkoja, että keskitettyjä suurten voimalaitosten verkkoinfrastruktuureja tietojärjestelmineen. Ylituotantosähköä voidaan käyttää nestemäisten ja kaasumaisten ilmastoneutraalien polttoaineiden tuotantoon. Suomi on parhaillaan siirtymässä kohti energiasiirtymän toista ja kolmatta vaihetta. Toinen vaihe ei kuitenkaan Suomen tapauksessa ole erityisen dramaattinen maan vesivoima- ja bioenergiaresurssien johdosta, samalla kun rajat ylittävä sähkönsiirtoinfrastruktuuri liittää maan osaksi pohjoiseurooppalaisia sähkömarkkinoita. Koska yksikään maa ei kuitenkaan toistaiseksi ole täysin siirtynyt kolmanteen vaiheeseen, monenlaisia haasteita on odotettavissa. Tästä syystä tämä tiekartta esittelee yli sata eri toimijoille kohdennettua suositusta uusiutuvan sähköntuotannon lisäyksen jatkamiseksi, näin syntyvien resurssien käyttämiseksi liikenteen ja rakennusten sähköistämiseen, älyverkkojen kehittämiseksi, jatkossa tarvittavan kansainvälisen yhteistyön tukemiseksi sekä energiasiirtymän tuomien vientimahdollisuuksien hyödyntämiseksi teknologian, infrastruktuurien ja konseptien avulla.

Fossil fuels, coal and oil are used for energy production around the world. Combustion of these fossil fuels produces gases and particles that affect air quality and climate. The CO2 emissions can be decreased by substituting fossil fuels with biomass and this substitution can further affect the particle emissions of the power plants. This thesis focuses on characterising particles of real-scale power plants with various fuels, from combustion to atmospheric dilution. The studied power plants were a combined heat-and-power (CHP) plant (combusting coal and a coal – wood pellet mixture) and a heating plant with three fuel mixtures. The particles were characterised mainly based on particle number size distribution and number concentration, using aerosol sampling from the superheater area of the boiler of the CHP plant, the stack of the CHP and the heating plant and the atmosphere surrounding the CHP plant.Measurements for the aerosol samples taken from the boiler indicated that the particles from the combustion of coal and the mixture of coal and industrial pellets had already formed in the boiler. The formation of the particles was studied by changing the dilution of the aerosol sample and by comparing the electrical charges of the particles in the boiler. The coal-combustion particles were around 25 nm in diameter. The addition of 10.5% industrial pellets to the coal caused the formation of a second particle mode, the soot mode (120 nm in diameter), in the boiler. In the heating plant, the addition of light fuel oil to heavy fuel oil had a similar effect on the oil-combustion particles. The particles from the combined coal-and-pellet combustion agglomerated and coagulated before reaching the sampling point in the stack. These processes, combined with the effect of an electrostatic precipitator, resulted the mean diameter of the particles to be 80 nm. Further, the flue-gas desulphurisation and fabric filters lowered the particle number concentrations. The particles measured inside the stack were also observed from the atmosphere before they were diluted to background concentrations. The flue-gas plume was measured in four occasions, in three wind directions and with four flue-gas cleaning and fuel combinations. These measurements resulted in the observation of a new particle formation in the diluting plume. In the atmospheric measurements, the concentrations of SO2 and CO2 played an important role in measuring the dilution process. In the heating-plant experiment, the characterization of oil-combustion particles showed that the lower fuel sulphur content decreased the particles’ hygroscopic growth factors.The atmospheric primary emissions of coal-fired power plants can be effectively lowered through flue-gas cleaning technologies. In this study, flue-gas cleaning was shown to affect the flue gas’s particle number and the mass concentration as well as its black carbon concentration. The cleaning did not prevent new particle formation in the flue-gas plume in the atmosphere, but it did reduce the potential for particle formation.

The research topic of this thesis is inorganic gases from combustion that form particles via gas-to-particle conversion. The particles formed in gas-to-particle conversion have an effect on fouling of the super heaters and corrosion in boilers. These are the main reasons for unscheduled shutdowns and tube failure. Aerosol particlesformed from inorganic gases are challenging to study in boiler conditions. To be able to measure the particles formed via gas-to-particle conversion, the related processes need to be isolated from the boiler to a smaller and easily controllable environment. The experiments of this thesis were conducted in laboratory environment. The most important facilities used were high-temperature chambers, particle sampling and particle instruments. The first high-temperature chamber is used for the vaporization of the reactants, and the latter is used to achieve the gas-to-particle equilibrium. Water solution of solid reactants is fed to the chamber in order to control the amount of reactants. In addition, different gases are fed to the chamber. The reactants used in this thesis were selected from black liquor recovery boiler process. Black liquor composition is highly affected by the quality of the wood used in pulping, and that is why the reactant concentrations should be controllable. Black liquor consists mainly of sodium and sulphur but also of chloride from the wood. The chloride has been observed to be problematic since it causes corrosion in recovery boilers. A sample was taken from the second high-temperature chamber by diluting it in three steps before the particle measurement equipment. The measurement results show two mode particle size distributions. Results indicate that one of the mode is formed in high-temperature conditions and the other in the dilution. It was discovered that alkali sulphate formation is the key component of the particle formation in the second high-temperature chamber. Indirect references of alkali chloride formation are observed by studying the nucleation mode. The nucleation mode particle number is decreased when temperature of the second high-temperature chamber is lowered because more alkali chloride compounds is transferred to the particle phase already in high temperature conditions.