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Dr Eng. Angel Penev, a distinguished engineer and researcher, holds a PhD from the Technical University of Sofia. He has earned multiple certifications in energy efficiency and photovoltaic plant construction. With a career spanning thermal power plants and Toplofikacia Sofia EAD, he currently leads the "Energy Efficiency and Renewable Sources" department, managing energy savings projects and integrating renewable energy.

Through this article, Dr Eng. Angel Penev explores the critical role of natural gas boilers in maintaining Bulgaria’s district heating system and ensuring energy security. He examines the challenges of balancing seasonal energy needs, the impact of geopolitical tensions on gas supplies and the integration of renewable energy sources. Dr Penev underscores the need for strategic energy management and prioritising district heating to sustain environmental and operational stability.

Energy security is critically important to many stakeholders, including policymakers, companies, consumers and the public, depending on an energy supply. Based on the many hypotheses, energy security is indeed highly context-dependent, but there is no widely accepted definition for now. The main definitions given in the literature can identify the following eight major energy security themes: energy supply, infrastructure, regulation prices,  societal effects, environment, law' government, energy efficiency and renewable sources. These topics have been actively studied in recent years in the broader context of Bulgaria's national energy policy. The scope of energy security has also expanded, with a growing emphasis on dimensions such as environmental sustainability and energy efficiency. 

Since the economic crises of the winter of 2008-2009, energy security has been a commonly discussed issue on the political agenda on a European and  Bulgarian level. In this period, the headline points out that Bulgaria is left with almost no reserves and unlike most of its neighbours, it didn't have an alternative to supplying Russian gas through Ukraine. The situation in the country drastically reduced supplies for consumers and stopped production. Losses to the industry are estimated at 250 million euros. The problem now is not different. Russia is a natural gas supplier to Europe. With the invasion of Ukraine, the European and global economies began to fight with the high energy prices influence into food markets, services, etc. 

"Natural gas boilers are essential for maintaining the sustainability of Bulgaria's district heating system, underscoring the need for seasonal balancing between the energy mix and supply security while prioritising district heating over other alternatives."

Toplofikacia Sofia EAD is the largest District Heating company in Bulgaria. The cold winter in the country means that heating is essential for energy security, comprising an average of 7 TWh/year or more consumption only for the capital. The company supplies district heating, the most common conventional heating, providing around 65 percent of the heat used in non-residential and residential buildings. The fuel supply in our thermal power plants is almost only natural gas, which is much more environmentally friendly, compared to other fossil fuels such as industrial heavy oil, petroleum, diesel, etc. District heating fuel supply has come to be competed mainly by different forms of air conditioning technology and decentralised natural gas boilers.

The national ecology has to realise that the combustion process in the thermal plants is the same as that of local domestic natural gas boilers. Therefore, the emission fields are the same and it makes no sense for some to pay for permissible concentration and for individual consumers not to. Besides the CO2 refrigerant, integrating many refrigerants also leads to environmental pollution in air conditioning,  heat pumps, HVAC systems and industrial refrigeration applications. Despite the ecological issues, we aim to integrate new generation secured district heating, renewable energy technology and electromobility and we will implement standard energy management ISO 50001. 

Diversification of fuel supply is the main problem that determines primary energy availability. Concerns about diversification and geopolitical issues include outbreaks of wars, destabilised regimes, or regional tensions that can lead to gas supply disruptions. Underground gas storage Chiren covers the seasonal fluctuation of natural gas consumption in the country and is one of the tools ensuring the security of the gas supply. The alternative source of natural gas is renewable energy production, which is also one of the main goals of the national government. However, if this does not include promoting production and using biofuels, most renewable energy technology can’t be used efficiently in Bulgaria during the cold winter. That is why investment projects in renewable sources in district heating still have a low percentage of Internal Rate of Return (IRR).

The main difference in the present energy security in Bulgaria's district heating companies is the high security based on the current Preventive Action Plan that was prepared regarding the measures for guaranteeing the security of gas supplies. The plan is consistent with the National Risk Assessment of the Republic of Bulgaria and was developed after consultations with the enterprises for natural gas, payment to organisations representing the interests of households and industrial customers of natural gas, including electricity producers and The National State Energy  Regulatory Commission. 

In conclusion, natural gas boilers have a crucial role in ensuring the sustainability of the district heating system and preserving the environment. Seasonal balancing between the energy mix and the security of supply is a critical action in energy management and it is crucial to prioritise district heating over other alternatives.