Energy recovery devices for reverse osmosis applications

  • Overview
  • Product range
  • Documents
  • Related products
  • How it works
  • Case studies

3-in-1 energy recovery device

The 3-in-1 Energy Recovery Device (ERD) optimized for sea water reverse osmosis applications. With iSave you get pressure exchanger, booster pump and motor integrated into one compact unit for high efficiency and short pay-back time.

The small footprint of iSave makes it a popular solution when the space is limited. When fitted with iSave, the Danfoss APP pumps produce more fresh water per square meter than any other system in the market.

iSave can be used in almost any SWRO application – land-based or marine, new or retrofit. The 3-in-1 design allows fast commissioning, continuous monitoring of performance and easy regulation to accommodate seasonal changes. Other isobaric devices have been known to cause over-spin and over-flushing that lead to poor process control and low efficiency. This is avoided with the active control possibilities offered by the iSave technology.

iSave captures hydraulic energy from the high pressure reject stream of the SWRO process and transfers the energy back into the system, drastically reducing the energy consumption regardless of flow rate and size of your SWRO system. Besides substantial energy savings, the iSave ERD also cuts capital expenditure by reducing high-pressure pump size, number of pipes and components thanks to its integrated design.

iSave ERD for reverse osmosis - Brochure - Danfoss

Superior energy recovery in SWRO

Danfoss iSave is a patented, high-efficiency Energy Recovery Device (ERD) that guarantees constant membrane feed in SWRO applications of any size – on land, at sea or on the move.

Features and benefits

Extensive application know-how

Competitive efficiency rates

Compact – pressure exchanger, pump and motor in one unit

Easy and service-friendly design

Simple and reliable with high uptime

Short pay-back time

iSave selection tool - Danfoss

iSave selection tool

Download the iSave selection tool for easy calculation and selection. Calculate amount and size of iSaves for your project.

Product range

  • iSave 21 Plus energy recovery device (ERD) for reverse osmosis applications
    iSave 21 Plus

    iSave 21 Plus is a powerful ERD for smaller plants with a water capacity of 110 to 350 m3 per day. iSave 21 Plus is designed for high reliability, low maintenance and reduced lifecycle costs.

  • iSave 40 energy recovery device - Danfoss
    iSave 40

    The iSave 40 consists of an isobaric pressure exchanger, a high-pressure positive displacement booster pump and an electric motor. Max. differential pressure: 5 barg/72 psig. Speed: 600 - 1200 rpm.


Type Name Language Valid for Updated Download File type
Data sheet iSave 50 -70 Data sheet English Multiple 03 Aug, 2020 2.3 MB .pdf
Data sheet iSave 50 -70 Data sheet Spanish, Castilian Multiple 29 Mar, 2021 2.4 MB .pdf
Brochure Superior energy recovery in SWRO English Multiple 01 Jan, 2015 1.6 MB .pdf
Brochure Superior energy recovery in SWRO Spanish, Castilian Multiple 18 May, 2018 1.2 MB .pdf

Related products

  • APP high-pressure pumps - Danfoss
    APP pumps

    The APP pumps are designed for SWRO in land-based and marine applications, offering the highest efficiency rates in the industry. The compact design, long service intervals and reliability of the APP makes it a first choice for small and medium-sized desalination plants.

  • APP S 674 high-pressure pumps - Danfoss
    APP S 674 pumps

    The APP S 674 pumps are designed for SWRO offshore applications, offering the highest efficiency rates in the industry - comes with API 674 and ATEX certification.

How it works

Wherever simplicity and space matter, iSave’s 3-in-1 design makes energy recovery as easy as it is efficient.

iSave’s unique design puts three key components of isobaric energy recovery exactly where they belong: right next to each other. So now engineers can configure RO systems that are simpler, smaller and easier to operate – not least in tight places like containers.

When installed with compact APP high-pressure pumps, the Danfoss pump-and-ERD package produces more fresh water per square meter than any other system on the market.

Case studies

  • The buried treasure of Jeju Island transformed into fresh water Danfoss
    The buried treasure of Jeju Island transformed into fresh water

    Krosys is a leading Korean firm with long experience in SWRO systems. Krosys had no doubt that the APP pumps from Danfoss would be the most energy efficient way to transform the "lava water" into fresh Water at the Korean Jeju Island.

  • Solar Power Danfoss
    Danfoss at the heart of new ultra-efficient RO plant that uses nothing but solar power without battery backup

    Mascara NT chose Danfoss pumps and ERDs to drive an RO plant whose only energy source is the sun. Specially developed for some of the world’s most arid and isolated regions, the new OSMOSUN system is designed to produce water so efficiently that it does not need energy storage. By eliminating costly battery packs, Mascara NT’s solar powered plant radically reduces total life cycle costs and enables clean water in locations completely off the grid.

  • Low energy and maintenance costs is key to success at plant in Bermuda
    Low energy and maintenance costs is key to success at plant in Bermuda

    ROCONSERVICES chose a Danfoss APP pump and two iSave energy recovery devices to form the heart of each of its two 180,000 gallon per day seawater RO units in Dockyard, on the west end of Bermuda.

  • SWRO Units Danfoss
    Danfoss iSave® ERDs at the heart of new, high-end containerized SWRO units

    Get to market fast with a containerized, low-maintenance high-performance SWRO plant. Pre-engineer it to be flexible enough to accommodate a wide variety of desalination conditions. And deliver at a good price.