The 4th generation central heating system integrates all available energy sources, renewable ones, and surplus energy from other sources. Moreover, energy accumulation and storage, as well as producer-user interactions ensures system flexibility and efficiency. The use of lower-temperature water leads to the reduction of heat loss in networks, which makes this kind of district heating become more accessible for all. When transitioning from the 3rd to 4th generation district heating system, it is important to simultaneously coordinate and ensure the smooth functioning of all existing systems and facilities. The transition from the current 3rd generation DH is a complex task that requires addressing the following aspects:

• How to ensure a sufficient heat transfer with a lower fluid temperature?
• How to adapt building heating systems for operation with lower heat transfer fluid temperatures?
• How to manage a smooth transition from higher to lower temperatures?
• What are the possible alternative production sources that do not use fossil fuels?
• How to ensure protection against Legionella bacteria?

Over the last decade, the movement towards net-zero has picked up at a rapid pace worldwide. Lithuania is no exception, having millions of renewable energy users across the country. With the help of solar power plants from renewable energy sources, an increasing number of organisations and independent users are producing electricity for their own needs. There’s no doubt that energy prosumers creates countless opportunities.

Thermal energy production from renewable energy sources is asynchronous. In most cases, the peaks in energy production do not coincide with the peaks in heat consumption. For this reason, measures are required to rebalance it.

One of the most convenient ways is heat storage tanks. These can be used for the accumulation of excess electricity produced from renewable energy sources. Thus contributing to the rebalancing of the power supply system. It is important to address the following challenges:

• Assess the potential of heat produced from renewable energy sources.
• Determine the optimal need for seasonal, medium-term and short-term storage tanks.
• Review possibilities of re-use of old infrastructure.
• Examine which direction of heat accumulation to choose: centralisation (central, general) or decentralisation (accumulation at the customer, distribution in the network).

One of the main challenges faced by water treatment companies is the recycling of sewage sludge which contains heavy metals, phthalates and bacteriological contamination. Doctors globally warn that phthalates have a strong negative effect on the endocrine system. Phthalate-contaminated environment may increase the risk of infertility, birth defects, cancer, diabetes, and obesity.

Various biomass fuels are burned in Lithuanian boiler houses. Biomass incineration inevitably generates a lot of process waste – ash. For example, the main CHP of VŠT generates approximately 18-20 tons of ash per day. It’s a lot of process waste, but if used wisely, it could be of benefit. Biomass ash could be used in agriculture or forestry and enrich the soil with macro- and microelements. It could also be used in the building and road construction sectors. However, macro-elements and heavy metals in the ash content are subject to maximum concentration levels, which may not be exceeded in pursuance of the secondary use of the ash.

Intensive urban development leads to a reduction of green spaces. One of the ways to restore it, is to turn roof spaces into nature or farm areas. Each plant-covered roof can become a part of this movement to restore the endangered nature. A building with a green roof improves heat insulation: the accommodation retains heat in winter, and keeps it pleasantly cool in summer. It also creates a series of ecological benefits such as additional oxygen release, air humidity regulation, dust neutralisation and rainwater utilisation. Cities can feed themselves, and create space for flora and fauna, gardening or even beekeeping.

In the long run, pipes wear out, and heat leakage is a fairly common problem for older infrastructure nearing the end of its service life (this is particularly the case for heat networks laid in impassable underground channels). In order to assess the real state of pipelines, it is necessary to monitor networks, humidity levels in cameras, ensure early detection and localisation of energy leakage. Reduced humidity content in underground channels extend the life cycle of a pipeline network. Measurement of the wall thickness of the pipe allows changing the worn networks up to a specified limit.

A residual heat map is a very useful tool to understand the potential of unused waste heat. The analysis of the heat-cooling economy carried out within the framework of the STRATEGO project of the European Union (EU) showed that the heat produced by factories and power plants alone, but not used and discarded as residual heat, would satisfy the entire heat demand of buildings in Europe and in some cases even exceed it. Heat mapping is a great way to assess the geographical location and potential of waste energy in the city. Many layers of analysis can provide a fairly complete picture of the supply, which facilitates energy planning and investment in infrastructure.

Publicly available data on the energy consumption of buildings along with the possibility of comparing them with data from similar facilities (the average and the most efficient renovated and the non-renovated buildings) would help the public access the state of the building and energy costs. This would encourage the user to look for ways and means to reduce the costs of heat energy and housing maintenance. 

The European Union (EU) cares about the well-being of the planet and is implementing a low-emission mobility strategy as well as the development of the infrastructure for alternative fuels. In this context, municipalities in Lithuania have to establish low emission zones in cities by 2023, where only zero-emission traffic is allowed. The promotion of environmentally friendly vehicles poses challenges not only for the development of green public transport, there are recharging points for electric vehicles to think of, the availability of alternative fuels in cities but also the identification, administration and technological aspects of low-emission zones.

An environmentally friendly lifestyle is gaining ground in Lithuania. The number of clean energy-using electric cars, electric and traditional bicycles, scooters and other environmentally friendly vehicles are increasing on the streets. What if not only charging infrastructure for electric vehicles but also electric bicycles, scooters was developed in the city? Or even if wireless charging modules were installed on roads, paths or in one of the traffic lanes? The battery of the vehicle would charge just while driving on this lane!

There are thousands of parking places on the streets of Vilnius, but searching for a free parking space often takes time, which also leads to an increase in CO2 emissions. In order to reduce these undesirable factors, one should know how many parking places are available in a given place at a given time, for example, in Zverynas neighbourhood on a working day at 5 p.m.