Techno-economic analysis of a PV/T waste heat–driven compound ejector-heat pump for simultaneous data centre cooling and district heating using low global warming potential refrigerants

Overview

The study presents a comprehensive techno-economic evaluation of an innovative compound ejector-heat pump system for simultaneous data-centre cooling and waste-heat recovery for district heating. The new system avoids the ejector pump by combining PV/T waste heat with an evaporative condenser as the ejector driving force, and compares several low-GWP alternatives to R134a (R515B, R515A, R1234ze(E), R290 and others) on COP, PUE, ERE/ERF, cost rate, payback and CO2-eq.

Hourly performance used real ambient and solar data for Valencia (Spain). The DHN water temperature rise across the condenser was fixed at 20 °C and condensing temperature varied from 50 to 70 °C. Metrics used were ERE = (Total Energy - E_reused)/IT power and ERF = E_reused/Total Energy. With R515B the system raised COP by 54% in cooling mode and 49% in heating mode, the largest gain among the refrigerants studied.

The system improved the data-centre PUE index by 10 to 19%; R515B gave the largest PUE reduction (quantified at 1.48) and the highest electricity saving, 84.1 MWh per year. R290 gave the highest ERF of the refrigerants examined. The shortest payback, 6.3 years, came with R515B, followed by R515A and R1234ze(E); these three also cut CO2-eq emissions most, by 49%.

Limits: a simulation for Valencia's climate and one system configuration; the design suits heat-pump-based reuse of low-grade data-centre heat in warm climates and does not transfer directly to cold climates or different DH temperatures. Its ERE and ERF equations match the standard metric definitions.

Key points

1. Hourly performance used real ambient and solar data for Valencia (Spain); the DHN water temperature rise across the condenser was fixed at 20 °C and condensing temperature varied from 50 to 70 °C.
2. Metrics used were ERE = (Total Energy - E_reused)/IT power and ERF = E_reused/Total Energy.
3. With R515B the system raised COP by 54% in cooling mode and 49% in heating mode, the largest gain among the refrigerants studied.
4. The system improved the data-centre PUE index by 10 to 19%; R515B gave the largest PUE reduction (quantified at 1.48) and the highest electricity saving, 84.1 MWh per year.
5. R290 gave the highest ERF of the refrigerants examined.
6. The shortest payback, 6.3 years, came with R515B, followed by R515A and R1234ze(E); these three also cut CO2-eq emissions most, by 49%.

Using it in design

• When combining data-centre cooling and heat recovery for district heating in one heat-pump system, select the refrigerant among low-GWP alternatives with COP, PUE, ERF and payback together.
• Report heat reuse with ERE and ERF (ERE = (Total − E_reused)/IT power; ERF = E_reused/Total).
• Set the condensing temperature from DH requirements (50-70 °C, 20 °C water rise) and label results with the warm-climate assumption.

Who should read it

Engineers combining data-centre cooling and heat reuse with heat pumps, and researchers evaluating low-GWP refrigerant options.

Document contents

1. 1 Introduction
2. System description, thermodynamic and economic model
3. Hourly simulation results: COP, PUE, ERE/ERF
4. Cost rate, payback and CO2-eq
5. Conclusions

Related standards

• EN 50600-4-6 (ERF)
• The Green Grid ERE

Read the document

Publication details

Authors

Ali Khalid Shaker Al-Sayyab; Joaquín Navarro-Esbrí; Angel Barragán-Cervera; Adrián Mota-Babiloni

Publisher

Mitigation and Adaptation Strategies for Global Change (Springer Science and Business Media LLC)

Year

2022

Volume

27

Issue

7

Pages

43

Document language

English

Source type

Scientific

Access

Open licence — downloadable

DOI

10.1007/s11027-022-10017-6

Licence

CC BY 4.0 — share with attribution

Licence evidence

doi.org

Citation