Izvleček
Dolvodno od Trbovelj je predvidena veriga sedmih pretočnih vodnih elektrarn z manjšimi akumulacijskimi bazeni, od katerih je HE Vrhovo že zgrajena in obratuje od leta 1996. Ker je Sava že v sedanjem stanju toplotno onesnažena zaradi odpadnih voda jedrske elektrarne Krško (NEK, približno 1300 MW_t odpadne toplote) in termoelektrarne Trbovlje 2 (TET2, 157 MW_t), do leta 2004 pa je predvidena zamenjava TET2 z novo TET3 (237 MW_t), je bila izdelana študija toplotne obremenitve spodnje Save. Razvita sta bila enodimenzijski in tridimenzijski toplotni model, slednji za obravnavo toplotne slojevitosti v bazenih vodnih elektrarn. Tridimenzijski model je nastal na temelju hidrodinamičnega modela PCFLOW3D, ki je bil dopolnjen z možnostjo simulacije toplotnega onesnaženja. Oba modela sta bila kalibrirana in zadovoljivo preverjena. Študija obravnava dve situaciji: “vsakoletne kritične razmere” (KRR), kjer je upoštevan srednji nizki pretok in atmosferski pogoji normalno vročega poletja, ter “ekstremne razmere” (EXR) z najnižjim opaženim pretokom Save in teoretičnim, zelo vročim poletjem. Povečanje toplotnega onesnaženja od 157 na 237 MW bo povečalo rečno temperaturo pri Trbovljah za 0,43 ^oC v primeru KRR in za 0,83 ^oC v primeru EXR. V Krškem se ta vpliv že zmanjša na 0,34 ^oC pri KRR in na 0,65 ^oC pri EXR. To ne bo povzročilo opaznejših omejitev obratovanja drugih energetskih objektov. Zaradi izgradnje 7 bazenov vzdolž spodnje Save se bo temperatura v Krškem v primerjavi z nezajezenim stanjem povečala za približno 1 ^oC pri KRR in do 5,3 ^oC pri EXR.

Ključne besede: toplotno onesnaženje, matematično modeliranje, reka Sava
Originalni znanstveni članek   UDK 519.87:504.4.054

Abstract
A chain of seven run-of-river hydro powerplants (HPP) with smaller reservoirs is planned on the Sava River downstream from Trbovlje. One of them, Vrhovo, was built in 1996. Nowadays, the Sava River is thermally polluted by the Krško Nuclear Power Plant at the lower end of the future chain of HPPs (NEK, cca 1300 MW_t of heat load), and the Trbovlje Thermal Power Plant at the upstream end of the future chain (TET2, 157 MW_t). As the latter is to be replaced by a new unit TET3 (237 MW_t) by 2004, an extensive study on the thermal pollution of the Sava River was prepared. A one-dimensional and a three-dimensional numerical model was developed, the latter concentrating on the description of the thermal stratification of future reservoirs. The 3D model evolved from the 3D hydrodynamic and pollutant transport model PCFLOW3D, by including the thermal loading phenomena. Both models were calibrated and satisfactorily verified. The study focused on two cases: “hot summer conditions” (HSC), with the average low discharge and with normal hot summer temperatures, and “extreme conditions” (EXC) with the lowest recorded discharge and the highest recorded temperatures during the last four decades. The basic conclusions of the research were: (a) An increase of thermal pollution from 157 to 237 MW would increase the river temperature in the HSC case by 0.43 ° K at the source of the pollution (0.83 ° K at EXC) and by 0.34 ° K at the end of the chain (0.65° K at EXC). However, this increase should not cause any serious operational limitations of other electricity producers. (b) Due to the construction of 7 reservoirs, the input cooling water temperature of the Krško NPP would increase by 1 ° K for the HSC case and by about 5.3 ° K for the EXC case, both compared to the present state.

Key words: thermal pollution, mathematical modelling, Sava River
Scientific paper   UDK 519.87:504.4.054