24.11.2022 51% of the heating system of the city of Bucharest was not functioning, which shows the inability of SACET (centralized heating system) to fulfill its purpose for which it exists, causing frustration and putting those connected to it again in a situation of finding an alternative, because they do not have hot water and heat

History of the system

The calculation of the efficiency of the cogeneration/cogeneration solution (combined production in one installation of thermal energy and heat in the CET) compares the fuel consumption of the CET (Electric Heating Plant) with the consumption of the thermal plant (CT) and the Thermo – Electric Plant (CTE), which produces the same amount of heat and electricity of energy, like CET. From the feasibility study on the CET fence, it was found that fuel savings and lower investment are possible if both types of energy are produced in the same energy equipment. In CET, for very cold periods when cogeneration cannot provide the required thermal energy, water heating boilers (CAF) are installed, which reduce efficiency, but are a cheaper option to overcome some load peaks than if the cogeneration equipment is designed for maximum load.

The choice of engineers in the 1960s for the transport of thermal energy to domestic consumers was a distribution system with separation of the primary agent from the CET and the secondary agent that goes to the consumers, in contrast to the Soviet system, where the primary agent is injected directly into the radiators. The connection between the two systems is made through thermal points (PT), which receive the primary agent from the CET through primary pipes and through heat exchangers and pumps transfer heat and pressure to consumers through secondary pipes, which depart from the PT to the owners. ‘ Associations or public institutions and private.

The advantage of the solution is that faults in the secondary network do not interfere with the operation of the primary network, without affecting other consumers fed by the primary network. Also, the heat agent in the primary is hot softened water 90-150 oC (chemically treated in CET, therefore more expensive), while the secondary agent is potable water 70-90 oC.

In order for all consumers to have thermal energy, the secondary network is designed hydraulically balanced with laminated diaphragms at the entrance to the consumers to ensure the flow of the heat carrier necessary for each and to avoid that the first consumer (unit) all the circulation through it of the thermal agent and nothing does not reach the latter. Each block type has an estimated heat demand and hydraulic resistance. Based on them, a short network balancing project is drawn up. The hydraulic resistance is calculated based on the design of the heating units of the unit, each radiator, elbow, valve and existing pipe. The distribution in blocks is vertical with pipes starting from the basement to the top floor in columns, all measured at the block level.

Regulation of the amount of heat is carried out in accordance with the external temperature and is selected quantitatively and qualitatively, a decrease in the external temperature implies an increase in the temperature of the coolant and pressure in the network.

Historically, the system was developed in the 60s with the installation of steam turbines and regulated Soviet industrial steam, heating and condensing outputs at CET Bucharest, CET Grozavesti and CET Sud. The system was expanded by building CET West and CET South groups 5 and 6 with steam turbines and controlled Czech heating and condensing discharge. The last CET was CET Progresu with Romanian DSL 50 steam turbines licensed after the Soviet ones from CET Grozavesti (PT 50).

The heating system was introduced in the same year, and in the 80s, in some areas, due to the increase in the number of blocks that had to be built to cover the housing needs of the workforce in Bucharest, many more units were connected in PT than in the original design . This, along with the primary supply of industrial steam, was one of the reasons for the chill that enveloped the apartments and offices of Bucharest residents in the last years of communism.

All CETs in Bucharest are owned through ELCEN by the Ministry of Energy, thermal energy is produced and sold on their fence to Termoenergetica, formerly RADET, which owns part of the primary networks, PTs and secondary networks owned by the General Council of the Municipality. Bucharest. The Ministry of Energy sells electricity produced in these CETs.

Since the 1990s, CET has faced a sharp decline in the sale of process steam due to the closure or reduction of industrial consumption, with the result that the production of thermal energy for industry disappeared, steam turbines were operated only to produce steam for municipal needs. cogeneration (heating and hot drinking water). With the disappearance of steam production for industry, the income of the CHP decreased, and the need for year-round operation disappeared. CETs began operating more frequently as CTEs condensed most of the steam during the summer, becoming economically inefficient as natural gas was more expensive than coal. It ended with the fact that in the summer the turbines working with the KAF were stopped. The exception was CET West, which in 2009 was successfully upgraded to a combined cycle that could also operate in cogeneration in the summer.

The current situation, starting from the consumer to the source

Secondary heat networks are unbalanced and do not provide the necessary heat, especially in small heating points, in addition, most owners have renovated their apartments and replaced boilers with new ones with different hydraulic resistance. Distribution pipes in the blocks were clogged, not replaced on time, as a result of which the hydraulic resistance changed. The regulation of the network is no longer appropriate, which leads to the fact that the circulation of the secondary heat agent no longer corresponds to the design, as a result, many consumers are left without the circulation of the secondary agent through the installations.

Quantitative and qualitative regulation can no longer be achieved, the pressure remains at a minimum level to avoid the rupture of the pipes of the primary and secondary networks, because the replacements were not carried out in time, and then the circulation of the coolant no longer corresponds to the design. .

Termoenergetica’s budget for 2022 is 2,745,372 thousand lei, of which subsidies in accordance with legal provisions amount to 2,112,638 thousand lei, i.e. the owner, the General Council of the Municipality of Bucharest, provides 76.9% of the budget through subsidies, and the remaining 24, 1% comes from payment for services that this company provides. All residents of Bucharest connected to the district heating system together pay approximately €126.5 million for this service, after which all residents of Bucharest and those not connected pay the difference of €422.5 million needed to keep the system running .

Pipe replacements have been delayed or out of place, and currently 37% of the heat supplied to CET in Bucharest is lost. From a simplified calculation (nominal efficiency of heat production multiplied by the efficiency of heat transportation to the consumer 63%), it follows that thermal energy is produced with an efficiency of 57.96% if it works with CAF (92% of the project) and in the case of steam turbines with efficiency 63.5% (82% of the project, taking into account the efficiency of electricity production of 32%). The yield is far from that required by the EU for highly efficient cogeneration and for which all electricity consumers in Romania pay the cogeneration contribution.

After redoing the calculations, it was found that the solution in which the TT is installed as close as possible to the consumer, and the current is purchased from the CTE, is more efficient than the CET, and, in addition, considering that in Romania electricity is produced from a mixture of resources (coal, nuts, hydro, hydrocarbons and renewables) is much cleaner to buy it into the system than to burn gas in this CET. Further decentralization at the level of the thermal wall installation provided a yield of 94% and a saving of approximately 36% of gas (including less harmful substances) compared to operation with CAF.

With the difference in saved gas, electricity can be produced in other sources that burn hydrocarbons or reduce consumption at the national level (unfortunately, investments are waiting for combined cycle plants here too).

Naturally, in most cities in Romania, the disappearance of the system occurred due to a cause-and-effect spiral: dissatisfied consumers who left the system (a first for industrial steam), a decrease in the income of the heat supplier, an increase in the price of the service, a further decrease in the number of consumers who believed that they were paying too much a lot for poor quality service, reduced output of the source of production due to partial load operation, repeated price increases and finally bankruptcy of the service company due to debts. A few big cities, Bucharest, Timisoara, Craiova, Iași, Ploiesti, Oradea, have escaped this thanks to generous subsidies and some reconstruction

Law No. 196 of July 12, 2021 on the communal heating service introduced provisions that allow local public administrations to prohibit disconnections from district heating systems, even if the service is poorly provided.

Residents of Bucharest need to warm up and wash, and the bureaucratic barriers established in the legislation do not solve this problem. Any centralized intervention/investment will take years. Calculations show that at current rates it will take at least 10 years, optimistically, to change the pipes in the primary networks, impact studies and feasibility studies will be done for district/district power plants, etc. promising himself that “someday it will be better.”

In the case of block thermal power plants, most owners’ associations cannot agree and support investments of such a scale.

In the new suburbs, thousands of apartment units were installed on the outskirts, and the gas distribution system did not collapse because most of the transport and distribution networks were sized to take on the gas consumption of industry, much higher than that of the population and public institutions, a gas consumption that disappeared with the closure socialist enterprises.

Some residents in houses with gas metering networks will install wall heaters regardless of whether they are allowed to turn off or not, although there is a legal right to do so, those without hot water will install boilers or instantaneous electrics. and little by little, with or without the will of government, consumption will decrease.

Those who do not have gas networks will have them installed, and the cycle of reducing heat energy consumption will continue even faster as the number of buildings to be thermally rehabilitated increases.

Many flats have lower gas consumption than designed because today there is an electric cooker and/or oven, so there is additional capacity available for the transport and distribution of gas directly on the inter-flat networks that can be used. In addition, some heat consumers will switch to electric heating only in the rooms they are in as a cost-saving method, shutting off the heat so that distributors do not register and reducing their consumption. Read the rest of the article and comment on Contributors.ro