INDEPENDENT ENERGY STORAGE CONSULTING

Energy storage.
From concept
to operation.

Pumped storage. Battery systems. Hybrid renewables.

Technical insight across storage technologies — helping utilities, investors and development partners make informed project decisions.

Discuss your project Explore the project portfolio

Dipl.-Ing. Tobias DertmannBased in Germany. Working internationally.Scroll to explore ↓

Rathkinda reservoir surrounded by wooded islands and hills in Sri Lanka — Rathkinda reservoir · Sri Lanka Hydro–solar hybrid assessment · Start 2021

01 / EXPERTISE

Different technologies.
One system perspective.

Pumped storage
hydropower

Site screening, feasibility, hydraulic concepts and operating strategies for new and existing pumped storage assets.

PSH

Battery energy
storage

Sizing, technology assessment, grid services and technical requirements for utility-scale battery storage.

BESS

Hybrid renewable
systems

Hydropower, floating PV, solar and storage — assessed together through operational and economic modelling.

HYBRID

Grid integration
& procurement

Technical due diligence, grid integration, Employer’s Requirements and tender evaluation support.

GRID

THE STORAGE PRINCIPLE

Water. Height.
Flexibility.

A motor-generator drives the pump-turbine to store energy in the upper reservoir. In generation mode, returning water drives the same unit to produce electricity.

Pump & store Generate & supply

Pumped-storage cutaway with upper and lower reservoirs, penstock, a vertical motor-generator and reversible pump-turbine, and a submerged connection to the lower reservoir — Reversible pump-turbine · Schematic cutaway, not to scale

02 / SELECTED WORK

International experience.
Specific project insight.

Hydropower intake basin beside a river in a steep mountain valley in Nepal — NepalStart 2025
Hydropower in Nepal
Plant visit for a study of hydropower refurbishment opportunities.

Aerial view of existing grid infrastructure and rocky hills at the BESS study site in Georgia — GeorgiaStart 2022
Battery-storage site assessment
Existing grid infrastructure and the surrounding landscape in Georgia.

Aerial view of Hosororo's red-roofed powerhouse and penstock surrounded by rainforest in Guyana — GuyanaStart 2016
Hosororo small hydropower
Powerhouse and penstock within the tropical landscape of Guyana.

PakistanStart 2026

Pakistan utility-scale battery storage

BESS sizing and technology advisory for feasibility and procurement preparation, including degradation, conceptual design and supplier-market assessment.

BESSGrid

CambodiaStart 2025

Cambodia utility-scale battery storage

BESS specialist support for project preparation and procurement, covering technical configuration, specifications and technical tender review.

BESSGrid

Zambia / Zimbabwe (Lake Kariba)Start 2026

Lake Kariba floating solar

Hydrometeorology and hydropower expertise for a floating-solar feasibility study and integration with the existing hydropower system.

HydroFPVHybridGrid

VietnamStart 2025

Vietnam renewable-energy hybrid facilities

Hydropower and energy-system expertise for assessment of hydro–floating-PV integration and operating flexibility.

HydroFPVHybridPVGrid

ArmeniaStart 2024

Energy storage and transition in Armenia

Energy-storage advisory and technical review covering batteries, pumped storage, renewable integration and the energy-transition roadmap.

PSHBESSGrid

GermanyStart 2025

Niederwartha industrial-load optimisation

Operating and economic simulation of pumped storage with industrial demand, assessing dispatch, market prices and peak-load coverage.

PSHGrid

From individual assets to national storage strategies.

Explore all project experience

PROJECTS ACROSS BORDERS

29 project countries.

Engineering experience across Europe, Asia, Africa and the Americas — shaped by different landscapes, assets and energy systems.

Explore the project portfolio

World map highlighting the 29 countries in REESSA’s project portfolio — Countries with project experience

View all 29 project countries

Armenia
Bangladesh
Burundi
Cambodia
Finland
Georgia
Germany
Greece
Guyana
India
Indonesia
Italy
Jordan
Kenya
Lithuania
Madagascar
Mexico
Mongolia
Mozambique
Nepal
Pakistan
Peru
Philippines
South Africa
Sri Lanka
Suriname
Vietnam
Zambia
Zimbabwe

03 / THE CONSULTANT

Engineering depth.
A broader energy perspective.

Dipl.-Ing.
Tobias Dertmann

Independent Energy Storage Consultant
REESSA Consulting UG

I’m Tobias Dertmann, a graduate engineer in mechanical engineering and renewable energy, and an independent consultant at REESSA Consulting. My background combines hydropower engineering with international project advisory, including earlier work with Vattenfall’s hydropower engineering team.

Today, I support utilities, developers and international development partners on pumped storage, battery energy storage and hybrid renewable systems. My work ranges from site assessment and feasibility studies to operating simulations, technical specifications and procurement support. Projects across Europe, Asia, Africa and the Americas have given me experience with very different assets, energy systems and local conditions.

I bring technical, operational and economic considerations together to help clients understand their options and make informed project decisions—from the first concept to the optimisation of existing assets.

TECHNICAL

Understand the asset.

OPERATIONAL

Understand the system.

ECONOMIC

Inform the decision.