Technical Feature
Heat Mitigation & Management
Solving Heat Issues in Ship Energy-System Flow – a Vital Part of the Decarbonization Mix
Deltamarin R&D Manager Mia Elg provides some new perspectives on a key decarbonization enabler that deserves much more attention as the ship machinery field becomes more complex.

Reducing greenhouse gas emissions in line with regulations will in practice consist of a broad combination of operational and technical means to save energy, exhaust gas treatment and, of course, adoption of clean fuels. This inherently complex mix is unavoidable, as uncertainty over availability and limited resources makes a wholesale shift to low-carbon fuels on a well-to-wake basis pretty unlikely.
As a result we will see ship machinery change in multiple ways: alternative fuels will involve new requirements for engines; new energy-saving technologies will enable operational engine loads (and even overall ship power requirements) to be lowered; there will be increasing use of fuel cells; and carbon capture solutions will likely also become prevalent as an intermediate decarbonisation solution.
Electrification is also set to continue. For example, plugging ships into shore power will be a requirement for certain ships in the future under the EU's Fit for 55 rules, while electric propulsion will also likely be the most attractive option when using green fuels.
What is certain is that ship machinery will become much more complex because we will constantly have to learn more about new main equipment and fuel qualities, as well as understand the many interrelations in overall system balance, including heat consumption – a key ingredient that hasn't drawn so much attention – but one I think it's a good time to highlight as we head into winter in the northern hemisphere.
Feeling the Heat
Heat consumption represents a considerable part – potentially up to 20% in some of the estimates I've worked on – of a ship’s total energy consumption. The main reason there hasn't traditionally been a strong focus on heat consumption processes is that waste heat from the ship’s engines satisfies most heating requirements. Consequently, additional heat generation typically represents only a few percent of a ship's total fuel consumption.
But as we develop new machinery, this balance will change. For example, what happens when a ship is connected to shore power and the engines are turned off? The immediate result is that you lose all waste heat production and you have to turn on the auxiliary (diesel-powered) boilers to generate heat, which involves emissions. So, plugging into shore power does not alone guarantee that a ship is zero-emission in port. Direct electrical heating of ship consumers is hardly practical as the shore power requirement could double in some cases, not to mention the Capex needed for equipment upgrades.
But it's not only in port that there can be an increase in boiler emissions. Take carbon capture, where chemical absorption to remove CO2 from exhaust gases is reckoned to have the highest maturity of the various available technologies, according to a report by the Oil and Gas Climate Initiative. The process is, however, quite energy-intensive, with heat consumption representing a large share of the energy requirement. The need to produce additional heat onboard increases fuel burn and will in turn reduce the net carbon capture rate.
It’s not all bad news though: new fuels and technologies also provide opportunities for heat recovery. Clean fuels that produce zero sulphur in exhaust gases enable the recovery of more heat in the exhaust stack compared to Heavy Fuel Oil (HFO), for example.
WATCH the interview with Deltamarin’s Mia Elg on Maritime Reporter TV:
Next-Generation Heat System Principles
As part of a proper focus on heat flows, here I want to outline some key principles to mitigate some of these problems, as well as maximise a ship’s fuel-saving potential.
Firstly, any joule of energy is equal, be it heat or electricity. If there is any risk of having to use electricity for heating, we have to focus on energy saving in heat processes. From a thermodynamic perspective, we should also try to match the onboard heat consumption with as low a temperature heat source as possible. This not only releases high-value heat for efficient recovery, but also enables us to better utilize the low-temperature waste heat sources onboard. In my view, we are used to serving a lot of ship heat consumption with unnecessarily hot temperatures.
Reducing heat consumption temperatures is also key to unlocking radical improvement potential when a ship is on shore power. For instance, heat pumps could be utilized to produce heat in port. Heat pumps require electricity but considerably less than direct electrical heating, enabling zero emissions in port could at much lower cost.
Keeping Temperatures Low
Furthermore, heat pump efficiency depends on the heat production temperature. Even though high-temperature heat pumps exist and are being further developed, from an economic perspective it is sensible to keep temperatures low. Heat pumps can also be applied to improve the energy balance in the case of carbon capture.
But it’s not only heat pumps that benefit from the 'low-temperature heat for low-temperature consumption' principle. Heat storage is also a viable solution to lower additional heat production needs in certain ship types and operation. One existing solution onboard is simply using hot water tanks, where high-temperature heat is utilized to heat the tanks and heat consumption temperatures dictate how much usable heat can be stored. There is also new development ongoing in phase-change materials, enabling better weight and volumetric efficiency for heat storing.
As the low-temperature principle also unlocks recovery and utilization of lower-temperature waste heat from a ship’s operating machinery, we have more opportunities for efficient waste heat recovery of high-temperature heat. Here we have several options such as Organic Rankine Cycles, steam turbines for electricity production onboard or absorption coolers for producing chilled power for air conditioning.
Conclusion
In summary, good design in heat systems can lead to less need for shore power utilization and also less fuel consumption at sea with efficient heat recovery. Neglecting this can lead to unexpected energy consumption onboard as a side-effect of commendable attempts to decarbonize another process. Heat integration using all kinds of heat recovery equipment including heat pumps and storage can be very powerful. Proper analysis is essential to maximize the benefits, starting with understanding the magnitude of heat flow available for recovery and consumption.
Ultimately, everything is connected: ship operation, available equipment and available fuels and other energy sources.

About the Author
Mia Elg is R&D Manager @ Deltamarin. Her 17+ year career has always had development and optimization of ship machinery and energy systems as the guiding star. Elg’s current role as R&D manager is related to leading the development of Deltamarin’s new products and services, in addition to consulting service sales. Her areas of expertise include: Thermal engineering, product development and productization of different energy- and environmental services, energy balance calculation, energy flow simulation and environmental impact assessment. In addition, she has led the development of zero emission ship machinery in several projects. She has a Master’s degree in Thermodynamics.