Energy Efficiency in industrial processes - the role of heat pumps

Feb. 06, 2015 | by Philippe Nellissen, Emerson Climate Technologies

Introduction

Over the last decades, heat pumps have witnessed significant improvements, allowing them to be recognised as a Renewable Energy Source technology. This came with the growth of heat pumps in the residential and commercial sectors. Consequently, they have become one of the tools to meet Europe’s 2020 energy targets.

In another area of application, the industrial sector has also worked on its energy and CO2 savings potential (driven by internal and external factors). Over the last few years, mainly short-term solutions were implemented but now the industry is showing more and more interest in long term solutions. Among the available technologies, people will most of the time look at Cogeneration, Trigeneration, high performance boilers….

However, the interest in re-use of wasted heat, with its substantial energy-savings potential, is also growing. The principle is to use this excess heat to reduce the total use of primary energy and thus reduce overall operational costs, assuming that the capital cost of the necessary installation does not exceed the profit of energy savings. In this process, industrial heat pumps can deliver substantial benefits. However, this technology remains unclear for a portion of the industry. How can I use the same heating technology as the one installed in my house? This lack of knowledge and understanding of their potential leads industrial heat pumps to be considered as the elephant in the room and too often unassessed in energy improvement projects. Although industrial actors have a rough understanding about them, they actually ignore heat pumps.

This paper tries to summarise the potential and the status of vapor compression heat pump technology in the European industry sector and to show that it exists, works and brings substantial benefits for the end-user.

What is the role of large heat pumps?

Four major parameters need to be considered prior to installing a heat pump:


The heat source:
brings a certain level of temperature that you want to upgrade to a higher temperature.

The heat need: is the reason and application for which the heat is needed.

The equipment capability: working with inadequate material is not a good solution.

The end-user vision: is perhaps one of the most important of the four elements. If people don’t have a clear view of what they want to achieve, then it will be difficult.

Picture 1: Parameters to be considered prior to the installation of an industrial heat pump

And last but not least, the fifth element is monitoring and evaluation to ensure return on investment.

Indeed we must admit that the installation of a heat pump requires an initial investment.  Sometimes, within a company the Operations department will struggle with the Finance department on this point. This is why the end-user vision is so important.

The Heat Source/Need and the Equipment Capability

Looking at picture 2, it is clear that there are different types of sources: air, ground, water, rejected heat at condenser from a refrigeration system, oil cooling, process waste like exhaust gas and many others.

It is important to know that right now we can use a heat source up to 70°C and the heat pump can upgrade it up to 90°C which is currently a standard and a well-established temperature level. Potential applications (heat need) are numerous and include district heating, scalding, pre-heating, process drying, sanitation, pasteurisation…

Picture 2: Sources and applications for industrial heat pumps

Moreover, “Heat pump” is a very generic term and behind it there are a lot of different possibilities and solutions depending on the technology (see picture 3), the type of system and mainly on the type of driving force. This paper will focus on the electrical engine driven vapor compression heat pump. 

Picture 3: Heat pump technologies


Graph 1 shows what can be achieved with a heat pump using the vapor compression technology (equipment capability).

Graph 1: Vapor compression technology: Capacity and temperature

Scroll compressors with HFC that can reach up to 150kW in the range of 70-75°C can be considered. Based on HFC or Ammonia and following operating conditions, single or twin screw and reciprocating technologies can reach up 90°C with different level of performances. There are also other types of refrigerants such as CO2 that can reach 90°C but for lower capacities.

In the future, two main R&D trends can be expected:

-       Improved efficiency (and reduced costs) for the existing temperature range up to 90°C;

-       Development of new technologies, new refrigerants allowing higher temperature for the whole capacity range.

Besides Natural refrigerants (such as Ammonia, CO2, Hydrocarbon…), the F-Gas Directive has driven the development of new refrigerants. They fit the existing temperature range but also allow for higher temperatures. These new refrigerants must abide by strong health and safety rules (toxicity, flammability) as well as on efficiency and design (high vapor density, low pressure) limiting thus high investments and operation costs. 

The end-user point of view

For the industrial end-user, what are the factors to be considered to make a decision for a heat pump? 

They are two types of drivers

-      Internal drivers for the industry and its daily business:

o  The Operations department trying to optimise the cost by unit of product;

o  The Finance department trying to optimise the monetary aspect of the business expenses

-      External drivers:

o  Actual influences, such as legislation

o  A less tangible (and certainly one of the most important ones) is the mindset of the end-user and /or decision maker

Graph 2: Industrial heat pumps - Factors to be considered

For the Finance department, the capital expenditure for a gas boiler is lower than for a heat pump of the same capacity. However if the heat pump is combined with a cooling application (i.e. in HVAC) then the difference between the cooling and the heating through a heat pump vs. the combination of a gas boiler and a separate refrigeration system is much lower.

Another important point is the return on investment. This is a rather complex calculation where the result will depend on the gas price for the savings estimation, the electricity price, the performance of your heat pump and also how much you will use the heat pump.

Graph 3: ROI calculation elements and impact

For the daily business of an industry, the operating costs are one of the key elements and are part of the calculation of the return on investment (ROI). For a rough assessment, the ratio between the amount and cost of electricity and the amount and cost of fossil fuel on the site gives the basic COP (coefficient of performance), which needs to be reached for an application to pay off.

Regarding policies and legislation, there is a trend towards to promotion of energy savings and consequentially towards heat recovery systems. Heat pumps are considered in the Ecodesign directive and Energy labeling directive (see picture 4) and are seen as a tool to meet Europe 2020 tagets. Heat pumps are more and more looked at by policy-makers.

Picture 4: Energy Label

For industrial players, this is less the case.  This has probably to do with the mindset of the end-users who seem to be better understand alternative technologies aiming at the same goal  (such as cogeneration, trigeneration, high performances boilers) as heat pumps and are consequently more incline to use them. The end-user belief in industrial heat pump reliability could however change this. The reliability of the heat pump is not just a concept or a dream. A large amount of heat pumps are already available and installed in the market and do deliver substantial benefits. Industrial heat-pump technologies are no more in the prototyping or field-testing phase and can be used now.

A first assessment of the Potential for the industry

Assessing the potential of Industrial Heat Pumps is not so easy. Although a non- negligible amount of documents cover this topic, they mainly present a  technico-economic analysis on specific case studies.    Graph 1 (based on 2012 input, analysis still under progress temperature level, TWh market)Source: EUROSTAT, 33 countries) shows a rough estimation of the heat pump energy amount split that can be installed in the European industry.

These figures are based on an estimation of the useful heat energy consumption in the industry segments, some assumptions on the available heat sources and on the temperature levels which need to be reached (heat need), as well as on the equipment capability (what is technically feasible). The graph shows that lower temperature would represent a large potential for industrial heat pumps.

 

Graph 4 shows that 80°C up to 150°C represent a non-negligible part of the potential. The type of applications corresponding to the temperature of 60°C could be washing applications or drying for small elements, local heating. Applications corresponding to temperatures up to 70-90° could once more be drying, pre-heating, boiling, pasteurisation, or even laundering or coloring. There are many possible applications for this temperature range.

In Graph 5, chemical, paper, food & tobacco represent more than 50% of the estimated potential. The range of temperature is different for them. In the paper industry, the high temperature potential is bigger than in the food and tobacco for example.

This is a first estimation for the potential and some comments need to be made:

·      A better understanding of the potential can be achieved, if more literature and data from other EU member states is taken into consideration and bottom-up calculations for different member states are carried out.

·      District heating is not included in this study even if for Space Heating, a part of it could also be supplied by district heating. For, sure this would increase significantly the number. In this estimation, district heating is not considered and would certainly increase the potential in the range of 60 to 100°C.

A concrete example


Picture 6 shows an example from the real world, operating at low temperature (60°C) for a food & beverage (dairy) plant in France. The project was managed by Cofely, France. The goal (end-user vision) for the plant was to decrease electricity consumption and to make gas savings by producing the heat for space heating and complete sanitary hot water through the combination of cooling and heating in one single installation as shown on picture 6.

Picture 5: Scheme of combined heating and cooling concept

The company achieved this by replacing the old refrigeration installation by a combined cooling and heating system (equipment capability), as you can see on picture 5, that generates chilled water (which was the main job of the previous cooling installation) and upgrades it to a higher temperature than the standard temperature of the refrigeration system in order to generate hot water (instead of rejecting the heat from the cooling installation to the atmosphere).

Picture 6: New Cooling (and Heating) Compression unit installation

The refrigeration system makes it possible to provide cooling capacity to the evaporator and heating capacity to the condenser (heat source, heat need). When 1000 kW of chilled water is produced at Vire, 1300 kW of energy is recovered at the same time and combined with just 100 kW of electricity to heat water to +60°°C. All the energy produced and used is fully recovered. A 150 m³ buffer storage unit allows energy to be used to produce hot water as needed by the process (particularly cleaning operations). With the old system, this water was heated by gas, which has a much higher carbon footprint. In addition, the heat produced was rejected into the atmosphere by a cooling tower instead of being recovered and reused. The new system saves 9000 m³ of water a year and has reduced use of the cooling tower, which with its plumes of steam was always perceived negatively by locals.

The new installation works in cooling mode one third of the time and in cooling and heating mode two thirds of the time.

Graph 6: Electricity consumption

Looking at the results with the combined heating and cooling system, even with the additional electricity consumption of 100 kW for the cooling and heating mode, the electricity consumption per ton of product has decreased by 4 %. Indeed, in cooling mode, the consumption decrease comes from the new cooling installation and during the cooling and heating mode, the decrease comes again from the new installation but also from the condenser fans and water pumps switched off at the condenser.

The same is true for the gas consumption by ton of product. The decrease is in the non-negligible range of 6.5%

In total, the Energy usage per ton of product decreased from 820 kWh/ton to 559 kWh/ton so around 32%.

From the financial point of view, the ROI of this installation was about two years. The end-user is already in the process of installing a second combined heating and cooling system in their plant.  This is a clear indication of success.

 

Graph 7: Gas consumption

Energy dependency, EU 2020 targets and more

Energy savings have a clear impact on energy security.

Graph 8: Europe share of primary energy imports


This graph 8 shows that Europe depends on energy imports for more than 50%. More than one third of all primary energy imports to Europe in form of crude oil, gas or anthracite coal originate from Russia. Any efforts to decrease this energy dependency should be welcomed to reduce the risk of disruption of supply.

 

 It is also to be mentioned that whatever the type of heat pump component (condenser, evaporator or compressor) that is looked at, the manufacturers on the market are mostly European-based.

Picture 7: Non-Exhaustive illustration of European industrial heat pump component suppliers

Considering the example here above on combined cooling and heating, on could look at how non-domestic heat pumps (or Industrial Heat-pump) can support the European energy targets. Until now, the emphasis has been mainly put on residential and commercial applications. However, a medium size capacity heat pump (on the industry level) of 2400 kW is equivalent of 400 houses running a 6 kW residential heat pump.

Moreover, because of return of investment expectations, the minimum efficiency requirement for the non-domestic heat pump is already higher than the residential one according to European standards. Consequently, the impact of CO2 emission reductions should be also higher (see picture 8).

Picture 8: Comparison of non-domestic heat pump and residential heat pump CO2 emissions

More heat pumps for industrial applications will definitely support the European energy objectives. It is to be noted also that in some cases, the electricity supply from existing (dedicated power plants, CHP…) and renewable energy (solar, wind…) installations could be an issue in term of overcapacity. Indeed, some installations (such as CHP systems) are used for generating heat and electricity. It can happen that the electricity production is higher than the demand because of high productivity of the renewable energy resources.  This strange situation leads to the fact that CHP systems must remain in operation for the heat supply but provide non-required electricity.

Conclusions

There are enormous opportunities for the European industry in combining heating & cooling with heat recovery or heat upgrading or heat recovery stand-alone. The heat sources, the heat needs and the equipment capability are already there.

Heat pump applications for the industry should not only be considered at 60°C. 90°C is already more or less a standard for the industrial heat pump business, especially along with natural refrigerants. For higher temperatures in the range of 100°C-150°C, it is just a question of time with the development of new refrigerants and with the improvement of technology using existing refrigerants.

But the most important is that industrial players need to get the right view and get the right mindset. End-users now have to change their view concerning the use of fossil fuel in their processes and also need to rethink their processes by asking the following questions: do you really need steam in your process? Perhaps you want a heat pump with steam because you are used to work with steam? Perhaps that hot water could be sufficient for your process? However, all possible solutions should be looked at.

One often considers only the heats pump in their satellite applications around their core process instead of looking at how to use the heat pump directly in their core process. We have to move forward in this direction and consider using heat pumps in the core processes where major savings are possible.

In terms of European energy targets, large heat pumps can contribute to the success and have to be recognised as an important part of the puzzle. Now the elephant in the room has become visible, it is time to take action.

Sources:

-      Application of industrial heat pumps Proven applications in 2012 for Megawatt+ Heatpumps within a technical, commercial and sustainable framework, Dave Pearson, Star Refrigeration Ltd, Philippe Nellissen Emerson Climate Technologies gmbH

-      Energy efficiency: la Compagnie des Fromages counts on innovation with Emerson technologies, Emerson Climate Technologies-Emerson Industrial Automation article, 2014

-      Huge energy savings achieved in a dairy plant thanks to an Emerson system solution, Emerson Process Management Global Exchange conference (April 2014)

-      The heat recovery potential in the French industry which opportunities for heat pump systems, Eugenio Sapora, Maxime Dupont,  EDF

-      Récupération de chaleur industrie _ EDF, 1er Congrès Français des Pompes à Chaleur, Eugenio Sapora, Maxime Dupont EDF

-      IEA Heat Pump Center Newsletter Vol 30 n°1/2012

-      Heat pumps in non-domestic applications in Europe:
Potential for an energy revolution, Chillventa Congressing 2014, Heat Pumps Challenges  Markets, Technology Research, Applications, Ir. MM Philippe Nellissen, Emerson Climate Technologies GmbH, M.Sc. Stefan Wolf, University of Stuttgart, Institute of Energy Economics and the Rational Use of Energy