The mantra at Salaspils Siltums Ltd. is that the best way to protect the future environment is by acting now. It is of utmost importance to actively do something about global climate changes every day at both national and company levels.
By Roberts Kaķis, Process Quality Engineer at Salaspils Siltums
Published in Hot Cool, edition no. 4/2021 | ISSN 0904 9681 |
The primary purpose of “Salaspils Siltums” is to reduce the utility CO2 footprint and become more independent of fossil fuels. Solar energy is clean – with no greenhouse gas emissions released into the atmosphere.
From 100% fossil to 90% renewable
Till 2012, Salaspils Siltums was purchasing heat from the adjacent cogeneration plant running on natural gas, while the rest of the energy was produced using natural gas. In this way, all the thermal energy transmitted to the heating network was made using only fossil fuels. In 2012, however, the company integrated its first plant, a 7MW wood chip boiler producing thermal energy using renewable energy sources.
To increase energy efficiency and the system’s overall effectiveness, in 2015, we decided to supplement the woodchip boiler with a 1.68 MW flue gas condenser. At that moment, these significant changes which Salaspils Siltums made left a remarkable positive impact on the environment- in 2016, total CO2 emissions decreased by 80% compared to 2011, and thermal energy produced from renewable energy resources was 55%.
Salaspils Siltums changed the system to control and monitor all devices used in heat production processes along with these changes. They also changed all heat pipelines with a total length of more than 20 km —all these changes allowed to decrease heat losses by more than 20% compared to 2011.
But in 2019, Salaspils Siltums took the next step towards green energy setting up a solar collector park with a total area of 21’672 m2, installing 1’720 solar collectors. Simultaneously, we built an 8’000 m3 storage tank for thermal energy and installed another 3 MW woodchip boiler with a 0,5 MW flue gas condenser to replace gas-produced energy during the winter months. In 2020 up to 90% of the annual thermal energy production was from renewable energy sources, including 20% solar energy.
But will we in Latvia, where there are not so many sunny days, be able to produce heat with the sun?
The most striking example of solar energy use at the European and global level is Denmark, where they installed the first solar collectors in 1988. The Danish model also inspired Salaspils Siltums, and evaluating the climatic conditions in Latvia, which are very similar to Denmark, we concluded that we could also set good results in the use of such technologies. But to be sure that it was, in 2017, Salaspils Siltums installed 87 solar panels on the top of the company’s building roof. That was a pilot project to examine how productive and efficient solar energy technologies would work in Latvia conditions.
The results were excellent, and now, solar panels are producing 23,5 MWh of electricity every year, which fully safeguards the needs of the administration. This experience served as an undisputed argument why it is justified to integrate solar collectors into the company’s production system.
Now the solar collector field has worked for two whole years, and each year the performance is improving, mainly because of the improvement of the management of the collector field. One of the primary skills that have improved is determining weather conditions and characteristics and predicting how they will change. This skill allows managing the processes in the solar collector field to make it perform as well as possible for each scenario.
Forward-looking construction with a view to the future
One of the most significant bottlenecks that this project has highlighted is that since this is the first large-scale solar project in Latvia that includes installing a solar collector field, the local experts haven’t experienced how to carry out such tasks. For that reason, one of the conditions for the project applicants was that it had to include two parties – one part experienced in working with multiple similar projects and another consisting of local experts.
The main aim of such conditions was to raise the competence of local experts. Here in Latvia, we would have the representation that would ensure in-service servicing for all the systems built within the framework of this project.
Before the pandemic, we organized several tours for all types of leads – pupils, students, local entrepreneurs, experts from abroad, etc. We are doing our best to teach all our knowledge to others interested in doing similar projects or who want to understand how it works and its benefits. We are also trying to share production data at every opportunity so that everyone who wants to know and familiarize themselves with solar technologies can do it.
Performance has been excellent.
In the first full year, when the solar collector field was on the agenda, it produced in total 11’088 MWh, approximately 19% of the total annual thermal energy demand in Salaspils city. The rest was made by wood chip boilers (59%), flue gas condensers (12%), and to cover the peaks – by natural gas (10%). After the first year, Salaspils Siltums experts researched how good the performance of the 1 m2 solar collector is. The results were surprisingly good – 1 m2 of solar collector annually produces 511,6 kWh of thermal energy. The yearly sum of global irradiation is appr. 1150 kWh/m2, which means that the efficiency of the collectors was almost 45%.
A significant amount of thermal energy from solar collectors is produced in 7 months of the year. From April to September, solar collectors made at least 1’000 MWh each month, and in March, it was very close – 989 MWh. The most productive month was May, when 1824 MWh were produced.
Compared to 2021, the overall produced energy has decreased – 10’023 MWh. The main reason is that the spring, August, and September were much colder than last year and cloudier. However, June and July were very sunny, and the collector field was quite productive – in June were 2’154 MWh produced, but in July were 2’200 MWh produced.
So Salaspils Siltums produced all demanded thermal energy only from renewable energy resources from April till the middle of August. It looks like no fossil fuels will be used to cover the demand of the city during autumn.
As much as it was the merit of the solar collector field, it has no less value to the accumulation tank. It was possible to store the thermal energy from the wood chip boilers in the accumulation tank. It allowed us to produce the energy for the peak loads not to have to use other fuels. The total power of the wood chip boilers and flue gas condensers are a bit smaller than the peak load for the thermal energy of the city.
The accumulation tank produces thermal energy in the time slots when the load is smaller and stores the difference between the produced energy and the load. For example, at night, when the load is small, it is possible to make more energy than needed. The difference goes to the accumulation tank, and in the morning, when the load reaches its peak, the required difference, that wood chip boilers with flue gas condensers can’t cover, is taken from the accumulation tank, which is filled up during the night.
An accumulation tank is an excellent piece of equipment, which is essential for solar thermal systems. But it also facilitates work for other technologies, as in the above example. During periods of maintenance of boilers, it is possible to fill the storage tank and not use fossil fuels at the time of stopping.
Cooperation between solar collectors and panels
The latest project from November 2021 of implementing a 110-kW solar panel field will cover the need for electricity that needs the solar collector field. This will allow producing thermal energy next summer without using any external energy sources. Electricity is required to ensure the solar collectors’ function of circulation pumps.
The whole project allowed a price reduction of thermal energy for the citizens of Salaspils city by 12,7%. Now in writing, the heat price is 48,2 EUR/MWh, independent of the natural gas market fluctuations. Green production is not only environmentally friendly but also beneficial for thermal energy producers.
For further information please contact: Roberts Kaķis, roberts@salaspilssiltums.lv