SUPERNOVA

Independent teaching preview by Teodor Dimov. This is an unofficial resource. Its use in H2START teaching is a proposal for discussion.

Hydrogen, step by step: an open teaching idea for H2START

I offer to build free, open, privacy-first teaching tools for H2START, the hydrogen centre at Trakia University in Stara Zagora: an interactive hydrogen chain, a teaching-stand model and a classroom exercise.

By Teodor Dimov. Nothing on this page is agreed with H2START or Trakia University, or endorsed by them.

The light dims. What changes first? Go to the exercise

Follow the chain

In about 10 minutes you can: trace hydrogen from production to use (2 min) · balance one chain and explain a trade-off (3 min) · see what the electrolyser and fuel cell do in the stand model (3 min) · tell what the model assumes apart from what would need measuring (2 min).

Data status labels

Each block carries one label. The labels differ by text, shape and border style. In this version everything is “Simulated” or “To verify”.

See the chain

Hydrogen goes through several steps before it does anything useful: electricity, then the electrolyser, compression and storage, transport, and finally a fuel cell or another end use. Each step loses some energy. When hydrogen is used on site, the transport step can be skipped.

Electrolysis: electricity splits water into hydrogen and oxygen. An electrolyser is the device that does this.

A fuel cell uses hydrogen and oxygen to make electricity, water and heat.

A load (electric load) is the part that uses the electricity, such as a fan or lamp.

Simulated Original schematic of an on-site chain (no transport step). No values are shown.

Schematic of a hydrogen chain, not to scaleLight reaches a PV source, which makes electricity. Electricity and water go into an electrolyser, which gives off hydrogen, oxygen and heat. Hydrogen goes to storage, then to a fuel cell that also takes in air (oxygen). The fuel cell gives electricity, water and heat. The output does not loop back to the input. Light PV / source electricity Electrolyser water in O₂ out heat H₂ H₂ storage H₂ Fuel cell O₂ / air in Electricity out water out heat out Output does not return to the input:less comes out than went in. Schematic, not to scale Schematic of a hydrogen chain, not to scaleLight reaches a PV source, which makes electricity. Electricity and water go into an electrolyser, which gives off hydrogen, oxygen and heat. Hydrogen goes to storage, then to a fuel cell that also takes in air (oxygen). The fuel cell gives electricity, water and heat. The output does not loop back to the input. Light PV / source electricity heat Electrolyser water in O₂ out heat H₂ H₂ storage H₂ Fuel cell O₂ / air in Electricity out water out heat out Output does not return to the input: less comes out than went in. Schematic, not to scale
Schematic, not to scale. General principles: U.S. DOE, Hydrogen production: electrolysis; Fuel cells. These describe general principles, not evidence of any real stand.

Legend

Two families: energy flows (light, electricity, heat) use filled arrowheads; matter flows (water, H₂, O₂/air) use open arrowheads.

  • Light — energy, long dashes
  • Electricity — energy, solid line
  • Heat — energy, dash-dot line
  • H₂ — matter, dotted line
  • Water, O₂ / air — matter, thin dotted line

The schematic as steps

  1. Light reaches the PV panel or another electricity source.
  2. The source turns part of the light into electricity; the rest becomes heat.
  3. Electricity and water go into the electrolyser.
  4. The electrolyser splits water: hydrogen (H₂) and oxygen (O₂) come out, plus some heat.
  5. Hydrogen goes into storage and waits there until it is needed.
  6. Hydrogen goes from storage to the fuel cell; the fuel cell also takes in oxygen from the air.
  7. The fuel cell makes electricity, with water and heat as by-products.
  8. The electricity out is used by a load. It does not flow back to the start.

Losses, and why this is not a loop. Every conversion loses part of the energy, mostly as heat: light to electricity in the source, electricity to hydrogen in the electrolyser, hydrogen back to electricity in the fuel cell. So you get back less electricity than you put in. The chain is not self-sustaining: its output cannot run its own input, and without light (or another source) it stops once storage is empty.

This version is qualitative: no numbers in the schematic or the exercise.

Exercise: The light dims. What changes first?

Simulated Choose an answer first, then read a sample explanation, change one condition and choose again. There is no score, no timer and no single right answer. Everything here is qualitative.

The light dims. What changes first?

This exercise was inspired by The Hydrogen Game, developed at DTU by Pernille Gøtz and colleagues as part of Green Skills for Hydrogen. Independent simplified adaptation, not affiliated with or endorsed by its author. No photos. Sources: https://greenskillsforhydrogen.eu/the-hydrogen-game-is-now-online/ · https://greenskillsforhydrogen.eu/trainings/hydrogen-game/ (accessed 2026-11-06).

The “colours” of hydrogen

Hydrogen itself has no colour. The colours are informal labels for how it was made. They aren't official categories. EU law uses terms like “renewable” and “low-carbon” hydrogen and RFNBO instead.

A label doesn't fix the emissions. Below are the ranges the IEA reports, in kg CO₂-equivalent per kg of hydrogen (life-cycle emissions to the production gate under the report’s method). The labels are listed alphabetically, not ranked. Green here doesn't mean “good”.

RES (renewable energy sources; BG: ВЕИ) means electricity from sources such as wind, solar, hydro or geothermal. IPHE is the International Partnership for Hydrogen and Fuel Cells in the Economy; the IEA (2023) report uses an IPHE methodology that does not count embedded emissions of equipment.

Read the ranges in context. Colour labels are shorthand for production routes. Reported emissions depend on inputs and on which stages the study includes. Compare ranges that use the same unit and cover the same stages.

Ranges, not rankings. Source: IEA (2023), Towards hydrogen definitions based on their emissions intensity, CC BY 4.0, pp. 8–9, 40, 48; Executive summary. Colour names: informal labels. Accessed 6 Nov 2026.

Same data as a table (kg CO₂-eq/kg H₂, IEA 2023)
LabelRouteRangeSource
Bluenatural gas with capture5–8 (~60% capture); 0.8–6 (>90% capture, not yet in operation as of 2023 (IEA))IEA 2023, p. 9
Brown/blackcoal, no capture22–26IEA 2023, p. 40
Greenrenewable electrolysis0 under the IPHE methodology used in IEA (2023); not a universal zero life-cycle valueIEA 2023, pp. 8–9
Greynatural gas, no capture10–14IEA 2023, p. 9
Pinknuclear electrolysis0.1–0.3IEA 2023, p. 40
Turquoisemethane pyrolysisabout 2–16IEA 2023, p. 48
Whitenatural hydrogenno figure available—
Yellow (meaning varies)grid electrolysisabout 24 (world-average grid); about 0.5 (very low-carbon grid)IEA 2023, p. 40

Under Article 29a(1) of Directive (EU) 2018/2001, energy from renewable fuels of non-biological origin (RFNBOs: renewable fuels of non-biological origin — an EU legal term for fuels such as hydrogen made with renewable electricity) can count towards Member States’ renewable energy shares and the targets specified in that provision only if using those fuels achieves greenhouse gas emissions savings of at least 70%. Delegated Regulation (EU) 2023/1185 sets the calculation method and a fossil comparator of 94 gCO₂eq/MJ. That works out to 28.2 gCO₂eq/MJ (derived: 94 × 0.3). [established; 28.2 derived]

Boundary of this citation: consolidated version of 16.07.2024 (CELEX 02018L2001-20240716). EUR-Lex PDF. Later amendments and the annex of Delegated Regulation (EU) 2023/1185 have not been read from a primary source in this preview.

A teaching-stand model

Simulated Simplified schematic of a teaching setup. The arrows show the sequence of conversions. Any readings from a physical demonstration are labelled separately with the measurement conditions. This page shows no stand parameters and no instrument readings.

Methods and limits

FAQ

What is this page, and how does it relate to H2START?

An independent SUPERNOVA educational idea by Teodor Dimov. It is an expression of interest and a proposed collaboration, still under discussion. It is not an official H2START or Trakia University page.

Where does the energy come from?

In this schematic, light drives a PV source that makes electricity. The electrolyser consumes electricity and water and produces hydrogen and oxygen. The fuel cell consumes hydrogen and oxygen from the air and delivers electricity, water and heat to a load.

Why can the same colour have different emissions?

Colour labels are shorthand for production routes. Reported emissions depend on inputs — for example, electrolysis on a high-carbon grid versus a low-carbon grid — and on which stages a study includes. See the Yellow range in the IEA (2023) table.

How does an electrolyser use electricity and water?

Electricity splits water into hydrogen and oxygen. The current sets how much hydrogen is made (Faraday's law).

What does a fuel cell do?

It uses hydrogen and oxygen to make electricity, water and heat.

Why does less energy come out than went in?

Every step loses part of the energy, and the losses multiply along the chain. See the exercise.

What do hydrogen colour labels describe?

Informal labels for the production route. They are not official categories and not a measure of emissions. Emissions are shown as source ranges.

Is there a 3D view?

Not in this version. The HTML/SVG schematic is the main view. A 3D view may come later; it is not included here.

Can I use it on a phone or with a keyboard?

Yes. Everything works with a keyboard. On a phone the schematic switches to a vertical layout.

Who created The Hydrogen Game?

Pernille Gøtz (DTU), in the Green Skills for Hydrogen project. This exercise is an independent, simplified adaptation inspired by it.

Which parts are simulated, observed or measured?

Everything on this page is a model. Nothing is a measurement of a real device.

Is there a confirmed workshop?

No. Any session is only a proposal.

How can I suggest a correction?

Email teodor.dimov.26@trakia-uni.bg.

Glossary

Hydrogen (H₂)
A gas that can carry energy from where it is made to where it is used.
Value chain
The steps from making hydrogen to using it, with storage or transport where needed.
Electrolysis
Electricity splits water into hydrogen and oxygen.
Electrolyser
The device that carries out electrolysis.
Fuel cell
Uses hydrogen and oxygen to make electricity, water and heat.
Load
The part that uses the electricity, such as a fan.
Storage / Transport
Holds hydrogen for later / moves it elsewhere.
Power
How fast energy is supplied or used at a moment.
Efficiency
The share of input energy that becomes the wanted output, in the part studied.
Emissions intensity
Greenhouse-gas emissions per kg of hydrogen (kg CO₂-eq/kg H₂).
RES / renewable electricity
Electricity from renewable sources such as wind, solar, hydro or geothermal (BG: ВЕИ).
IPHE
International Partnership for Hydrogen and Fuel Cells in the Economy; methodology used in the IEA (2023) report for some zero values.
Renewable hydrogen
Hydrogen from water electrolysis using renewable electricity. [established, COM(2020)301]
Low-carbon hydrogen
Fossil-based hydrogen with carbon capture, and electricity-based hydrogen, with significantly lower life-cycle emissions. [established]
RFNBO
EU legal term for renewable fuels of non-biological origin; rules in Reg. 2023/1184 and 2023/1185.

Sources

Contact and next step

Feedback on clarity, scientific wording or fit for a teaching session is welcome: teodor.dimov.26@trakia-uni.bg. No forms, no tracking, no cookies.

Ask about the teaching activity or suggest a classroom trial.