UHRIG Energie

FAQs

We have put together some answers to the most important questions concerning wastewater heat.

If you would like to know more, just ask us.

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Project development and business model

What business models are used to implement wastewater energy projects?

Most projects are realized on a contracting basis, with the end customer being offered a fixed price in cents/kWh for heating/cooling. This promotes transparency and price stability. Customers are in no way involved with the operation or procurement of the system. They simply receive heating and/or cooling at a fixed price without having to give it another thought.

What permits do I need to obtain for my project?

The operator of a wastewater energy recovery plant requires the permission of the wastewater grid operator, who assesses whether a system for recovering wastewater energy may be installed in a certain section of the wastewater grid. The deciding factor for the wastewater grid operator is that such a system does not impede the wastewater system in any way, which we can guarantee with our Therm-Liner solution. As a company that has been working in pipeline construction for 60 years, we know all the ins and outs of pipelines. Before a system is put into operation, all the parameters are set out in a usage agreement. We are happy to provide templates for such usage agreements.
The wastewater grid operator does not need to carry out any additional cleaning, maintenance, or monitoring in the section of the pipeline used.

How do you ensure that the system always achieves the specified output?

Our heat exchanger systems are always aligned with the lowest possible dry weather flow, which is the lowest level of wastewater that can flow through the pipeline. This ensures that the systems always perform reliably. And during the project development stage, we also measure the volume and temperature of the wastewater in question, which allows us to optimize and safeguard the system.
Because the volume of wastewater can be precisely calculated and forecast for decades to come, the use of wastewater to generate energy is extremely reliable. A particular benefit is the fact that the temperature level of wastewater recovers quickly, even after large amounts of energy have been harvested. On the one hand, this is thanks to new inflows into the wastewater system and, on the other hand, the constant absorption of heat from the ground. This means that a large number of wastewater energy recovery systems can be installed in a single wastewater grid. It is just important to maintain a certain distance between the systems. A so-called “recovery section” that is around two to three times the length of the system itself should be located downstream of each wastewater heat recovery system.

Are the systems planned and operated on a monovalent or a bi-/multivalent basis?

Most of the systems we realize today are bi- or multivalent. This means, for example, that the base load can be covered with wastewater heat, while peak loads are covered by district heating, gas or/and CHP plants. Our heat exchanger systems are always aligned with the lowest possible dry weather flow, which is the lowest level of wastewater that can flow through the pipeline. This ensures that the systems always perform reliably.
A further possible application of wastewater heat is feeding it into heating networks. Energy from wastewater is an appealing green energy source for district or local heating, whether this is a cold or warm network. We have already realized some projects of that kind.

At what point should I get in touch with UHRIG?

If you want to check a location as to its suitability for extracting energy from wastewater, please contact us. The street, house number, and postcode are all we need. If you already have information regarding the wastewater situation at a selected location, we can then find out how much energy you would be able to extract there and give you an initial cost estimate.

What is the target group for wastewater energy?

Wastewater energy is an economical option for the heating and cooling demand of any building with an energy requirement upwards of approx. 50 kW, which is equivalent to about 15 residential units. The largest system realized to date has a withdrawal capacity of 2.1 MW. It supplies 450 residential units and additional commercial units. As a heat pump technology, wastewater energy aims for a temperature level of 35 to 55 °C / 95 to 131°F,
but there are also a number of projects in which higher temperatures are fed in. It is always a question of who the competitors are and what the next best option is. Wastewater heat is also particularly suitable for municipal or city heating networks. These local or district heating networks can be both cold and warm networks.

What do I need to take into account when developing my project? What do I need?

If you are considering using wastewater energy for a real estate project, the following three questions are key:

► Where is the nearest municipal wastewater pipeline?

► How much wastewater does it carry?

► What is the temperature of the wastewater?

Some wastewater grid operators provide energy maps online, while others will supply you with the information if you ask them. We are happy to help you if you would like to check a certain location.

Please note: Heating and cooling with wastewater energy is already a feasible and competitive option. Up to 15% of the heating requirements in the buildings in Germany can be covered by wastewater heat. Wastewater energy meets all the requirements of the German Building Energy Act (GEG), which defines wastewater energy as renewable energy.

Installation and operation

By how much does wastewater cool down as a result of energy extraction?

Heat is extracted from the wastewater in the course of energy recovery. Generally speaking, the wastewater cools down by 0.5 to 1K. If a larger amount of wastewater than the dry weather flow runs over the system, the cooling effect is lower. Although the wastewater cools down, the temperature is restored very quickly, thanks to the inflow of new wastewater and the absorption of ambient heat through the pipeline. The key factor, therefore, for treatment plants, which generally require wastewater to have a certain minimum temperature, is how much heat the last heat exchanger upstream of the treatment plant extracts from the wastewater and how far away it is from the treatment plant. The energy extraction in the network upstream of that one has no bearing on the treatment plants. The fact that the wastewater cools down therefore does not pose an obstacle to wastewater energy recovery.

How do you ensure that the specified output is always achieved?

The required extraction rate must be consistently available. Accordingly, our systems are designed to work even at the lowest volumes and temperatures. Conversely, this means that our Therm-Liner systems almost always work under better conditions, thereby reducing the power required by the heat pump. However, they must be installed at a low point in order to be able to supply energy reliably under all circumstances.

What kind of maintenance or cleaning do Therm-Liners require?

Heat exchangers are usually cleaned in the course of regular pipeline cleaning work. Like the wastewater pipeline, the heat exchanger system can be cleaned using a conventional flushing vehicle. Ideally, streamlined rinsing nozzles (such as Ei 120) should be used, and the maximum flushing pressure should be 160 bar / 2320.6 psi. The system can also be cleaned manually, e.g., with a pressure hose or high-pressure cleaning equipment. Generally, it does not require much cleaning. Customers can also take advantage of our monitoring services that constantly assess the systems.

Is it necessary to interrupt the regular wastewater service in order to install a Therm-Liner?

No. Our heat exchangers are installed during ongoing operations. If necessary, the dry weather flow is ensured by means of water retention, i.e., a bypass is laid for the duration of the installation work, thereby preventing any disruptions. The need for and extent of water retention measures are determined in the course of the mandatory inspection in the project planning stage. Guaranteeing the uninterrupted operation of the wastewater system during installation is a major factor in the success of the technology.

How long does it take to install a Therm-Liner?

It takes between one and four weeks to install a heat exchanger system, depending on its size. In certain cases, one or two additional weeks may be needed for the construction of the interface, i.e., the pipe connecting the pipeline and the heating room. The duration is different for each project. The only circumstance that could delay the installation of the heat exchanger modules is when heavy rains fill the pipeline with massive amounts of water. Currently, you must reckon with a lead time of two to three months for the manufacture and installation of a Therm-Liner system.

How do wastewater grid operators feel about this technology and about its being installed in their pipelines?

Wastewater management is a public service. The top priority is to ensure uninterrupted operation. Heat exchangers in the wastewater pipelines will therefore only be approved if they do not impede or restrict the wastewater management in any way. Our Therm-Liner system fulfills that requirement, with heat exchangers that can be installed during ongoing operations and that do not need any maintenance or cleaning.
Wastewater grid operators in many cities are now approving the installation of heat exchangers. Some of them charge a usage fee to cover the small amount of attendant paperwork. This fee also makes wastewater grid operators generally more open towards wastewater heat and the energy potential in their own pipelines. Some wastewater grid operators have already created energy maps to illustrate that potential and have put them online. This allows anyone to check specific locations as to the feasibility of wastewater energy recovery there.
One reservation that wastewater grid operators often have is that the wastewater cools down when energy is removed. Although it is true that thermal energy is removed from the wastewater when energy is extracted, thereby cooling it down, the temperature is restored very quickly, thanks to the inflow of new wastewater and the absorption of ambient heat through the pipeline. The key factor, therefore, for wastewater treatment plants, which generally require a certain minimum temperature of the wastewater, is how much heat the last heat exchanger upstream of the treatment plant extracts from the wastewater and how far away it is from the treatment plant. The energy extraction in the network upstream of that one has no bearing on the treatment plants. The fact that the wastewater cools down therefore does not pose an obstacle to wastewater energy recovery.

Can heat exchangers also be installed in pressurized wastewater pipelines?

Heat exchangers can also be installed in pressurized wastewater pipes. The only disadvantage compared to gravity pipelines is that the installation of the heat exchangers requires some underground engineering. Pressurized pipes must be opened up, and usually a whole section is replaced by a new pipe section with an integrated heat exchanger. This makes economic sense anytime a new pressurized pipeline is being built or an older one is being rehabilitated. However, if neither of these scenarios apply, the economic viability depends on the extent of the underground work required, which is different for every project. In the case of gravity pipelines, because they are walkable from a certain size upwards, the installation of heat exchangers does not require any underground construction work. This is why installing heat exchangers is generally worthwhile in these types of pipes.

How are the heat exchangers or systems installed in the wastewater pipeline?

The heat exchangers are installed in accordance with the corresponding requirements of the DWA (German Association for Water Management, Wastewater, and Waste). These requirements are defined in DWA technical bulletin no. 114. The heat exchanger modules are not set in concrete, but are rather fixed in place with brackets. These brackets are attached to the pipe wall with an HKD expansion anchor. The maximum bore depth is 40mm, and bore diameter 12mm. The anchor is screwed in flush, using countersunk screws (DIN 7991 M10x25). All fixing elements are made from grade 1.4404 stainless steel to prevent interactions. Deflector plates protect the components and connecting parts from sludge and damage. These deflector plates and the cladding of the feed and return pipes are also made from 1.4404 steel. The transition areas from the bottom of the pipe to the first element and from the last element are each protected by run-up and discharge ramps preventing any coarse matter from getting caught. These ramps are also made from 1.4404 steel.

Therm-Liner: The heat exchanger modules from UHRIG

What makes the Therm-Liner from UHRIG so special?

Our Therm-Liner can be installed in any pipeline while it is in service, without disrupting it in any way. This is the basic prerequisite for being allowed to use the wastewater grid in the first place. As a civil engineering company that has been working in pipeline construction for 60 years, we know all the ins and outs of pipelines. Accordingly, we have the best expertise when it comes to installing our solutions, which is a major factor in their success and efficiency. The Therm-Liner system is patented and certified. We are the world market leader in the field of wastewater heat exchangers and are currently rapidly expanding our production and installation capacity.

Where are the heat exchanger modules manufactured?

The Therm-Liner modules are manufactured at our headquarters in Geisingen, Germany. They are made, patented, and certified in Germany. Every Them-Liner solution is tailored to the project at hand, as the situation is different in every pipeline. We take these unique conditions into account when planning the system and also double-check everything during an on-site inspection. And before moving on to the realization stage, we also measure the volume and temperature of the wastewater in question to verify the wastewater grid operator’s data. In this way, we ensure that the Therm-Liner will perform reliably.

What are the components of the heat exchangers modules and how do they work?

The Therm-Liner heat exchangers are made from 1.4404 stainless steel. The surface is specially designed to achieve the maximum possible energy extraction rate per m² of surface and to keep the build-up of sludge to a minimum. The formation of a biofilm is inevitable to a certain extent, which is something we always take into account when planning a project. Our systems are usually installed at the minimal dry weather flow, so that the required output is guaranteed at all times.
The water in the module is colder than the wastewater in the pipeline, so the wastewater running over the module heats it up. This means that a heat transfer takes place even though the wastewater never comes into contact with the water in the module. The stainless steel acts as the conductor. The heated water flows from the module through a pipe to the central heating system which forms the feed and return line to the heat pump. The systems run on tap water or a mixture of water and glycol. One kWh of heat generated in this way consists of 75% energy from wastewater and only 25% from electricity – this is energy efficiency and climate protection in action.

Energy legislation

What permits must I obtain to be able to recover wastewater energy?

The operator of a wastewater energy recovery plant requires the permission of the wastewater grid operator, who assesses whether a system for recovering wastewater energy may be installed in a certain section of the wastewater grid. The deciding factor for the wastewater grid operator is that such a system does not impede the wastewater system in any way, which we can guarantee with our Therm-Liner solution. As a company that has been working in pipeline construction for 60 years, we know all the ins and outs of pipelines. Before a system is put into operation, all the parameters are set out in a usage agreement. We are happy to provide templates for such usage agreements.
The wastewater grid operator does not need to carry out any additional cleaning, maintenance, or monitoring in the section of the pipeline used.

By how much can I reduce my CO2 emissions with wastewater energy?

Heat generated from wastewater is CO2-free. Only the electricity needed for the heat pump needs to be taken into account, which is increasingly being generated on site as part of the projects themselves, e.g., by means of photovoltaic systems, meaning that zero CO2 is emitted. In view of the fact that we see green energy sources being added to the general mix of energy every day, wastewater energy will be completely CO2-free in the medium term, even if a conventional electricity mix is used.

What is the primary energy factor of energy from wastewater?

Wastewater has a primary energy factor of 0; added to this is only the primary energy factor of the auxiliary energy needed for the heat pump. Taking the heat pump into account, the primary energy factor of wastewater heat in new buildings is generally between 0.4 and 0.45. All of the KfW bank’s energy efficiency standards can be met with wastewater heat.

Where is the use of wastewater energy legally regulated?

Wastewater energy meets the requirements of the German Building Energy Act (GEG) just as well as any other renewable energy source. Wastewater energy is defined as renewable energy in Germany and the EU. In Germany, this is laid out in the GEG. At EU level, wastewater heat has been recognized as renewable energy since 2018 under the Renewable Energy Directive (2018/2001/EU).

General

What potential does wastewater energy have overall?

Energy from wastewater could cover up to 15% of the heat demand in the building sector in Germany alone. This would mean 4 to 12 million people could receive eco-friendly heat recovered from wastewater. The potential is especially high in urban areas.
As the market leader, we have already realized about 120 projects, most of which are in Germany. They vary in size, ranging from 20 kW to 2 MW. Wastewater network operators are also increasingly looking to exploit the potential of wastewater energy. Some provide online potential maps to make it easier for people interested in developing projects, while others develop and operate projects themselves.

What pipelines are suitable for the recovery of wastewater energy?

UHRIG Therm-Liners can be installed in both old and new pipelines. The prerequisite is a nominal diameter of DN 400 / 16’’ upwards. Smaller sizes do not carry enough wastewater, and the installation of the system is more expensive. In addition to gravity pipelines, there are also pressurized non-man-entry pipelines. Wastewater heat recovery is possible in pressurized pipes, but as a rule the heat exchanger must be affixed all the way around the pipe, or a section of the pipe must be replaced by a pipe section with an integrated heat exchanger. Pressurized pipes are usually only adapted for wastewater energy recovery if the installation of the heat exchanger coincides with the renovation or new construction of a pressurized pipe. Ultimately, however, a case-by-case assessment is necessary and advisable for every project.

What are favorable conditions for the recovery of wastewater energy?

Cities and urban areas are good locations, as are towns that are near a sufficiently large wastewater network. The relevant questions are always the same:
► Where is the nearest municipal wastewater pipeline?
► How much wastewater runs through it?
► What temperature is the wastewater?
Some wastewater network operators provide energy maps online. Others supply this information on request.
Wastewater energy meets all the requirements of the German Building Energy Act (GEG), which defines wastewater energy as renewable energy.

How much does wastewater energy cost?

Depending on the specific local situation, the investment costs for generating wastewater energy using the UHRIG Therm-Liner are around €500 to €1000 per kW heat exchanger output. These costs include the planning, building, installation, and commissioning of the heat exchanger system.
In good locations, heat production costs for wastewater energy generation are approx. 7 to 8 ct per kWh heating output, depending on the electricity costs incurred by the heat pump used. This is a full-cost calculation that includes
► capital costs for heat exchanger including the connection pipes
► capital costs for the heat pump
► pump and heat pump electricity
► service and maintenance
This amount is often incorrectly compared with pure procurement costs, such as gas rates. Capital costs for heating and infrastructure must also be factored in for fossil fuel heating systems. Projects are often realized on a contracting basis, and end customers are offered a fixed price in ct/kWh for heating or cooling. This promotes transparency and price stability. Customers are in no way involved with the operation or procurement of the system. They simply receive heating and/or cooling at a fixed price without having to give it another thought.

Is wastewater a reliable energy source?

Yes. Wastewater has an average temperature of 10 to 12°C / 50 to 54°F in winter and between 17 and 20°C / 63 and 68°F in summer. This temperature represents heat, or rather thermal energy, that can be used to heat buildings in winter and cool them in summer. Wastewater energy is a renewable energy source that is largely overlooked but has the potential to make a significant contribution to climate protection in the heating market. Because the volume of wastewater can be precisely calculated and forecast for decades to come, the use of wastewater to generate energy is extremely reliable. A particular benefit is the fact that the temperature level of wastewater recovers quickly, even after large amounts of energy have been harvested. On the one hand, this is thanks to new inflows into the wastewater system and, on the other, to the constant absorption of heat from the ground. This means that a large number of wastewater energy extraction systems can be installed in a single wastewater network. It is just important to maintain a certain distance between the systems.

How does the Therm-Liner recover energy from wastewater?

The Therm-Liner heat exchanger is a stainless steel module with an integrated water circuit. We can install our modules in any wastewater pipeline with a nominal diameter of DN 400 / 16’’ upwards. The water in the module is colder than the wastewater in the pipeline, so the wastewater running over the module heats it up. This means that a heat transfer takes place even though the wastewater never comes into contact with the water in the module. The stainless steel acts as the conductor. The heated water flows from the module through a pipe to the central heating system which forms the feed and return line to the heat pump. The systems run on tap water or a mixture of water and glycol. The heat pump, using a small amount of electricity, then makes the wastewater energy usable. One kWh of heat generated in this way consists of 75% wastewater energy and only 25% electricity – for optimal energy efficiency and climate protection.

Where and how is energy recovered from wastewater?

Wastewater energy can generally be recovered in three places: first, “in-house”; second, from the municipal wastewater system; and third, at the treatment plants. UHRIG’s Therm-Liner primarily harvests energy from the municipal wastewater system, owing to the large amount of energy there and the many potential consumers in the vicinity. By comparison, the wastewater energy potential of an individual house is small and therefore not very cost-effective. Wastewater treatment plants can generate vast amounts of energy, but once they have been recovered, they still need to be transported to potential consumers. The recovery of energy from the wastewater system is therefore a decentralized approach with the clear objective of directly connecting source and consumer.

Why recover energy from wastewater?

Wastewater is a permanently available high-volume source of energy. Millions of households, as well as commercial and industrial facilities discharge huge amounts of thermal energy into the sewer systems in the form of wastewater. This energy can be recovered and used with the help of wastewater heat exchangers.

Wastewater energy can be used to both heat and cool buildings. It is CO2-free and a game-changer for the heating turnaround. Up to 15% of the heating needs in the German building sector can be covered by energy harvested from wastewater. This would mean 4 to 12 million people could receive eco-friendly heat recovered from wastewater. The potential is especially high in urban areas.

What is the target group for wastewater energy?

Wastewater energy is an economical option for the heating and cooling demand of any building with an energy requirement upwards of approx. 50 kW, which is equivalent to about 15 residential units. The largest system realized to date has a withdrawal capacity of 2.1 MW. It supplies 450 residential units and additional commercial units. As a heat pump technology, wastewater energy aims for a temperature level of 35 to 55°C / 95 to 131°F, but there are also a number of projects in which higher temperatures are fed in. Wastewater heat is also particularly suitable for municipal or city heating networks. These local or district heating networks can be both cold and warm networks.

FAQ

UHRIG Energie worldwide

Energy recovery from wastewater is a technology from Germany with enormous export potential. We have already built and installed more than 120 heat exchanger systems in eight European countries. And two years ago, we established our U.S. subsidiary and have been active in the U.S. and Canada ever since.

In Germany alone, up to 15% of the heating requirements in the building sector can be covered by wastewater heat. That means heating for 4 to 12 million people. Wherever there are people, there is both wastewater and high heating needs – a perfect balance between supply and demand. 

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