Country: Greece


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Description: The Centre for Renewable Energy Sources and Saving (CRES) is the Greek organisation for Renewable Energy Sources (RES), Rational Use of Energy (RUE) and Energy Saving (ES). CRES has been appointed as the national co-ordination centre in its area of activity. CRES was founded in September 1987 by Presidential Decree 375/87. It is a public entity, supervised by the Ministry of Environment and Energy and has financial and administrative independence. Its main goal is the research and promotion of RES/RUE/ES applications at a national and international level, as well as the support of related activities, taking into consideration the principles of sustainable development. The Centre is managed by a seven-member Administrative Council, which includes representatives from the General Secretariat of Research and Technology (Ministry of Education and Religious Affairs, Culture and Sports), the Public Power Corporation and the Hellenic Federation of Enterprises. CRES has a scientific staff of more than 120 highly qualified and experienced multi-disciplinary scientists and engineers. Its organisational structure comprises of the following units:

  • Division of Renewable Energy Sources
  • Division of Energy Efficiency
  • Division of Energy Policy and Planning
  • Division of Development Programmes
  • Division of Financial and Administrative Services

Since 1992, CRES is located on its wholly owned premises in Pikermi, Attica, where in addition to over 2000 square meters of main office space, it has experimental outdoor installations, specialised laboratories for energy technologies, a mechanical shop, conference rooms, a library and maintains a strong computing infrastructure. CRES has installed a demonstration Wind Park in the area of Agia Marina in Lavrio, Attica. The Wind Park is connected to the distribution network and has an installed capacity of 3MW. In the facility of the Wind Park, CRES operates the Park of ENergy Awareness (PENA), a new demonstration site for Renewable Energy Sources. In PENA everyone has the opportunity to observe real small scale RES plants in operation, while the young visitors can learn about environmental friendly technologies through innovative educational tools.
The Department of PVs and Distributed Generation of CRES is part of the Division of Renewable Energy Sources (RESD). RESD employs 40 scientists and engineers, focusing its activities on the design, support and execution of European and national RTD programs for the development of economically viable and environmentally friendly RES/RUE/ES technologies. The Department of PVs and DG cooperates systematically with organisations for the promotion of PV technology and Distributed Generation, such as EPIA and actively participates in European initiatives, e.g. the Electricity Networks of the Future (Smart Grids) and the European Technology Platforms for Photovoltaics (PV–TRAC) etc.

Battery Testing Laboratory

Description: Aim of the battery laboratory is the performance evaluation and characterisation of batteries operating under specified conditions, battery testing according to international standards (such as capacity or endurance tests) and the development of guidelines for the improvement of battery usage depending on the application.
Static Equipment
Description: Battery cycling unit for testing of battery banks up to 300V, max. current rate ±100
Description: Two battery cycling units designed for 12V battery systems and features a maximum current capability of ±300A
Description: Two battery cycling units designed for 12V battery systems and features a maximum current capability of ±50A
ELPRA SA. Discharge tester
Description: High rate discharge tester designed for the cold cranking test of 12V vehicle batteries. Its maximum discharge current is 1500A
Description: Life-cycle tester featuring six circuits capable of cycling a cell of 0V to 5V maximum and 0A to 1A current. Designed for testing small rechargeable AA size batteries, such as Li-Me, Li-ion etc.
Schlumberger SI359551E
Description: Single cell voltage measuring system capable of simultaneous monitoring of maximum 80 battery cells of 2V each
Description: Battery temperature control system for the temperature regulation of a battery in the range -10°C to +60°C. Temperature control is fully automated and the bath dimensions are 1.80m x 1.10m

Electric Vehicle Laboratory

Description: CRES is actively involved in testing, evaluation and dissemination of Electric Vehicles (EV). CRES has designed, developed and evaluated a Simplified Monitoring System (SMS) for performance monitoring of EV fleets with built-in GPS capable of performance evaluation and fleet management. CRES has received a patent for the SMS. CRES is also carrying out EV performance, energy consumption, battery testing and related studies. It also possesses laboratories for EV battery and electrical subsystems testing, such as battery units and battery management systems. Last year CRES participated in a report prepared for the Ministry of Environment, Energy and Climatic Change, titled: “Investigating ways for the development and penetration of electric vehicles in Greece."
Technical specifications (PDF)

Distributed Generation Laboratory (DG-Lab)

Description: The department of PVs and Distributed Generation of CRES is involved in applied research, mainly regarding power/energy balance issues at distribution system level. In the frame of the department’s research activities, the Distributed Generation Laboratory has been developed, which consists of two main facilities: the Hybrid system/Microgrid test site and the PV systems laboratory.
Experimental Microgrid:The Hybrid Power Plant and Microgrid laboratory is designed for studies on the performance of stand‐alone and interconnected microgrids, but it can also serve as an emulator of autonomous weak grids, such as the power systems of islands. The microgrid’s backbone is a low voltage, 3‐phase network to which all DER components are connected. The interconnection of the cables allow, among others, the ad hoc introduction of lumped parameters such a resistors and inductances which emulate the characteristics of distribution lines. The system is designed with a capability of hosting devices up to 20kW.
PV Systems Laboratory: It is divided into three laboratories each specialised on one type of components of a PV system, namely PV testing lab, Power Electronics lab and Battery testing lab. The PV Testing laboratory is equipped with hardware, intended for the characterisation of PV cells, modules or arrays, the power electronics laboratory is concerned with the testing of inverters used in PV systems, and evaluation of their suitability as DER equipment and the battery testing laboratory focuses on the characterisation of batteries operating under specified conditions, referring to battery testing according to international standards.
The laboratory is in operation since 1993 and currently run by 6 employees.
Technical specifications (PDF)

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Static Equipment
PV panels
Description: Panel with 1.1kW, panel with 4.4kW (single axis tracker)
PV inverter
Description: Inverter 1.1kW and inverter 2.5kW (both single phase)
Battery bank
Description: Bank with 60V/690Ah, bank with 96V/400Ah (both lead-acid OPzS)
Battery inverters
Description: 4.5kW, 3 single-phase units
Diesel genset
Description: 12.5kVA/400V, stand-alone operation
Load bank
Description: #1: 13.5kW resistive and 2.5kVAr capacative, 3-phase, #2: 100kVA resistive/inductive load
Reverse osmosis desalanation unit

Description: 3.5kW
PEM fuel cell
Description: 5kW (DC)
Fuel Cell inverters
Description: 2.5kW, 3 single-phase unity in 3-phase configuration
Description: 240V, 50Hz
Power analyser
Description: Monitoring of 3-phase voltage, power and frequency
SCADA modules and controller
Description: Interbus
SCADA console
Description: LabVIEW
Solar simulator
Description: Class ‘A’, xenon-lamp system
Environmental chamber
Description: #1: 5m³, -40°C to +80C, #2: 1m³, -20°C to +45°C<
Long-term outdoor PV tester
PV array simulator
Description: 400V/25A
Grid simulator
Description: 12kVA, 3-phase
Power charge/discharge controllers
Description: 300V (DC), 300A
High-rate discharger
Description: 12V, 1500A
Temperature controlled bath
Description: Up to 40°C
Static and Mobile Equipment

Power meter
Description: One for input/output power of devices and efficiency measurements

Power quality meterDescription: For monitoring of voltage current waveforms/harmonics etc.

IV tracerDescription: For up to 100kW PVs

Photovoltaic frames testing laboratory

Description: This Infrastructure also applies for the topic "Module and system performance"

Power electronics laboratory

Description: Testing the performance of inverters and other power electronic devices e.g. measurement of the inverter efficiency (curves or contour graphs), the MPPT efficiency, the inverter output power quality (T.H.D, current injection), or testing inverters regarding requirements for connection to the grid (anti-islanding protection, leakage current protection).
Technical specifications (PDF)
Static Equipment
Pacific Power Source ASX Series
Description: Three phase grid simulator for PV inverter tests. Main features: 1-12kVA, 1 or 3 phase operation
Sorensen DHP 200-25

Description: Two DC power supplies with electronically controllable output used as PV array or other types of DER simulator
Froment Load bank

Description: Three phase fully automated adjustable resistive-inductive load (up to 100kW)
Yokogawa WT2030

>Description: High precision power-meter for measurement of DC/AC circuits power as well as for the acquisition of efficiency curves of power electronics devices (e.g. inverters)
Mobile Equipment
Dranetz BMI Power Guide 4400

Description: Portable power quality analyser with the ability to measure harmonics, thd, transients and monitoring as osciloscope
PV testing laboratory

Description: Evaluation of PV performance, ranging from a single cell to large arrays either outdoors (in the field over an extended period of time or by performing single shoot measurements) or by using a solar simulator (control irradiation and temperature) and an environmental chamber (control humidity, UV irradiation and temperature).
Technical specifications (PDF)
Static Equipment
Spectra-Nova MT-Series solar simulator

Description: Simulation of insolation profiles for AM1.5 (Air Mass 1.5). 1.6m x 0.9m useful test area with 5% uniformity
NewSun Technologies PL200

Description: PV Module Laminator – 1.3m x 0.8m useful lamination area
Mobile Equipment
h.a.l.m. elektronik GmbH cetisPV-CT-F1

Description: Field IV curve tracer equipped with temperature and irradiance sensors, for the outdoors IV curve acquisition of PV modules or arrays for PV power up to 100kW
Solar radiation measurements laboratory

Description: This Infrastructure also applies for the topic: Module and system performance
Static Equipment
SCI TEC Instruments Two axis positioner
Description: Two axis programmable positioner for accurate irradiance sensing
Simulation and Optimisation Tools
  • Matlab/Simulink-grid simulations for different scenarions of RES penetration in distribution grids
  • ATPDraw – grid simulations for different scenarions of RES penetration in distribution grids

CRES upgraded the SCADA system of the experimental microgrid. The newly installed software allows the interconnection of the existing SCADA with Matlab/SIMULINK, thus enabling the testing and evaluation of more complex control algorithms

Testing Services
  • Performance evaluation and characterisation of distribution grid components, i.e. load controllers, inverters, control algorithms, power quality issues
  • Investigation of microgrid operation scenarios including islanded or grid-connected op-eration and Demand Side Management strategies, energy and cost optimisation studies
  • Evaluation of control architectures, i.e. central, distributed, decentralised control schemes
  • Characterisation of PV cells, modules, panels etc. in terms of I-V curves and conform-ance with relevant standards
  • Characterisation of PV inverters performance in terms of efficiency and protection and conformance with relevant standards
  • Characterisation of battery cells and conformance with relevant standards
Standards Compliance
IEC 61727 (for the PV systems testing)
Quality Management
All laboratories comply with the common DERri test protocol [EC FP7 2009-2013].
Recent Publications

This study deals with the implementation and evaluation of a Model Predictive Controller that performs a cost optimization of the operation of a microgrid. The algorithm was implemented tested on our experimental microgrid at CRES during the Transnational Access activity of EU funded project DERri (FP7-no. 228449)

  • M. H. Syed, E. Guillo-Sansano, S. M. Blair, G. M. Burt, A. M. Prostejovsky, E. Rikos:
    Enhanced Load Frequency Control: Incorporating Locational Information for Temporal Enhancement
    IET Generation, Transmission and Distribution, Vol. 13, Issue 10, 21 May 2019, p. 1865 – 1874, (doi: 10.1049/iet-gtd.2018.6603)
  • Cabiati, E. Rikos, A. Guagliardi, R. Lazzari:
    Experimental validation of Adaptive FCC and BRC functionalities for the proposed ELECTRA Web-of-Cells
    CIRED 2018 Workshop 2018 on microgrids and local energy y communities, Ljubljana-Slovenia, June 7-8, 2018, paper no. 227
  • H. Saelle, A. Morch, E. Rikos, S. M. Canavese, M. Kosmecki:
    Utilization of distributed energy resources’ flexibility in power system operation – Evaluation of today’s status and description of a future concept
    53rd International Universities Power Engineering Conference, UPEC2018, Glasgow-Scotland, September 4-7, 2018, paper no. 329

last updated: 23.10.2019

Centre for Renewable Energy Sources and Saving (CRES)