We have detailed below a list of Frequently Asked Questions that we hope will answer any queries you may have. Please contact us should you need to discuss any aspect of the Arbor ElectroGen biomass CHP system.
Technical
Q. Is this process wood incineration / burning?
A. No, and it certainly should not be confused with this type of process. It’s a thermal gasification process that extracts a gas, with useful energy content, from the wood, such that it can be used to cleanly generate power, heating, hot water and chilled water if appropriate.
Q. How does the gasification process work?
A. Put simply, the wood undergoes a controlled thermo-chemical reaction at high temperatures within a sealed vessel with the addition of a carefully managed level of oxygen which produces the gas.
Q. How does it produce electricity?
A. The gas produced is used in a reciprocating engine – essentially a reciprocating or internal combustion engine similar to that found in commercial vehicles. This drives an alternator to produce electricity. This process creates heat from the engine (which in a commercial vehicle is cooled via the radiator).
Q. Can the excess heat from the reciprocating engine be used?
A. Yes, this is a very valuable source of energy and can be used to either heat or cool building (via an absorption chiller).
Q. What is the best way to increase the efficiency of the system/process?
A. There are two efficiencies, electrical generation and heat recovery. When combined an overall efficiency of 65% plus is achievable. Please speak to a LowC specialist for more details on how this can benefit your scheme.
Q. What sizes are available?
A. Arbor ElectroGen is available in the following sizes:
- Arbor ElectroGen 130 – produces 130kW of electricity and 150kW of heat.
- Arbor ElectroGen 250 - produces 250kW of electricity and 325kW of heat.
- Arbor ElectroGen 500 - produces 500kW of electricity and 750 kW of heat.
The above outputs are based on assumed caloric value of the wood used as feedstock.
The process can accept a variety of alternative fuels, in various forms and depending on the levels of calorific values the outputs will vary. For example we can utilise straw, expeller (rape seed husks), Miscanthus etc . For more details on what can be used and how please contact a LowC specialist.
Q. I need more energy than your largest unit; can they be installed in multiples?
A. Yes, one of the major advantages is that the Arbor ElectroGen system can be installed and configured to suit the site output demands. For example we could use a combination of generation and combined Heat and Power (CHP) units. This will deliver a very high resilience on availability and an extremely robust case for redundancy in terms of maintenance and downtime ensuring production of energy compared to single unit applications. All of the principle elements of the plant are modular designed around the use of Off-Site Manufacture to allow flexibility of output capacity, plant resilience and systems adaptability.
Q. What’s the heat-to-power ratio?
A. Alternative methods of electrical generation from biomass technologies suffer horribly from an abundance of heat and have heat-to-power ratios from 3:1 up to 5:1, i.e. 5 units of heat for every one off electricity produced, e.g. biomass boiler / steam-turbine; Stirling Engine; high speed turbines - with the consequential dumping of the excess heat and loss of a useful renewable resource.
The heat-to-power-ratio range of Arbor ElectroGen is between approximately 1.15:1 and 1.5:1, meaning that the system is far more efficient in the production of the all important electricity to combat carbon reduction, so there’s more opportunity to utilise the heat without dumping it.
Q. Have the Arbor ElectroGen systems been proven commercially?
A. Yes, the Arbor ElectroGen system is a commercially-proven technology. It’s been developed by one of the world’s leading research experts in the field and demonstrated at countless commercially-run sites throughout Europe the Americas and the Far East. The development reference list extends over 30 years.
Q. Can the gas be stored if the engine system is not running?
A. No, the gas cannot be economically stored on site
Q. What happens to the gas when the gensets are undergoing maintenance?
A. In the event the solution only includes one engine, the gasifier output is temporarily reduced and the minimum level of gas is then flared off. However in the event the scheme is configured with 2 or 3 engines running at 50% - 75% capacity (turn-down) to allow maintenance and provide extremely high levels of availability guaranteeing revenue streams, then it is highly probable that the gas would be utilised 100% of the time.
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Site / Visual / Appearance
Q. What size footprint does the plant and storage require?
A. A typical Arbor ElectroGen plant would require a footprint of 144 square metres, excluding fuel storage and service / access roads / yards.
Q. How high is the building?
A. The building is approximately 7-9 metres tall for a 130 kW unit rising to 10-12m for a 500 kW unit.
Q. How high is the flue/chimney?
A. Since the flue gases are much cleaner than either natural gas fuelled CHP or a biomass boiler (heat only) installation we do not envisage that the flue will be much higher than the building height. All flue systems will be subject to a detailed analysis to ensure long term emission risk implications on the operator are mitigated. We are highly conversant with the issues relating to the Clean Air Act and Air Quality Objectives, and can take care of all associated flue planning considerations for you.
Q. Can the gas flare be seen and is there a visible flame?
A. No, the flaring of the gas during system start up or engine shut down need not be seen.
Q. What is the building’s fabric constructed from?
A. The visual appearance of the building is very flexible and can reflect the environment in which it sits, from rural timber clad to commercial rain screen systems. The frame and walls of the building will be constructed to suit the performance requirements suitable for spatial, structural, acoustic, air flow and materials handling performance requirements. Where possible, LowC would seek to construct the building using local, sustainable materials.
Q. What other site requirements does the plant have?
A. The plant needs a three-phase electrical connection, water supply and mains drainage for foul and storm water discharge. If heat top-up and/or back-up boilers are required as part of the installation, then natural gas or oil for off-grid installations may be required. Either a telephone line, broadband or GSM connectivity will be required for the remote monitoring of the installation.
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Commercial
Q. I have heard of the terms ROCs and FITs, what do they mean and are they applicable to the electricity generated by the Arbor ElectroGen system.
A. ROC stands for Renewable Obligation Certificate. FIT stands for Feed in Tariff.
ROCs are applicable to the Arbor ElectroGen technology
ROCs are applied through Government legislation at differing levels depending on the type of technology applied. The Arbor ElectroGen system attracts 2 ROCs per MWh generated.
Q. Does the Arbor ElectroGen system qualify for payments under the ROCs scheme and what is that worth?
A. Yes, it qualifies for 2 ROCs for electricity production whether this is consumed on site or exported.
Currently each ROC is worth around £50/MWh, which forms an extremely valuable revenue stream for the owner.
Q. Does the Arbor ElectroGen system qualify for payments under the Renewable Heat Incentive (RHI) scheme?
A. Yes, classified as ‘advanced conversion technology’ it currently attracts a payment of 6.5p/kWh for installations with a used thermal output of less than 200 kW. Above 200kW the incentive payment stream has not yet been established, however based on current policy and guidance it is highly likely that this will be extended to higher levels of generation. Like many others LowC await clarification by the UK Government.
Q. I have heard of grandfathering. What does this mean?
A. Grandfathering is the term applied through legislation which guarantees that the ROC banding category or in the case of the RHI a value (index linked), are guaranteed for 20 years. This provides the perfect case for bankable revenue streams to support an investment (as is the case for PV or wind turbine installations under current FITs.)
As an emerging technology, Arbor ElectroGen falls within the ‘advanced conversion technology’ category and thus qualifies for 2 ROCs per MWh of electricity generated. This is fixed for a 20 year period from the commissioning of a qualifying CHP generating station to protect the investment made.
Q. We only need electricity – is it economic and what happens to the heat produced from the engine?
A. Even if you only require electricity, the economics compared to other renewable electricity technologies available e.g. wind, PV or hydro are superb. Similarly when compared to traditional small scale biomass electrical production through boilers and steam turbines, the economics of the Arbor Electrogen system are also unsurpassed, making the Arbor ElectroGen solution the perfect choice for small scale and even for schemes over 5MW.
In the case where no heat is required on site we would engineer electrical generation only. This however involves ‘losing’ the value of the heat. Ideally, we would help you to find a consumer for the heat in your immediate vicinity.
With the recent introduction of the district heating subsidies in England this can also prove extremely viable. Please call a LowC specialist for more information.
Q. How can I utilise the Arbor ElectroGen system to add value to land development schemes?
A. When compared to alternative technologies that may be under consideration using the extremely high carbon reduction deliverables of the Arbor ElectroGen system, producing both heat and electricity through decentralised generation is a massive advantage in many ways.
Firstly, the carbon savings to the development are enormous for the investment cost. (£ invested versus kg CO2 reduction delivered).
Secondly, there is far less resistance to this type of technology from Planners than wind turbines, or indeed heat-only biomass boiler district heating schemes.
Thirdly, the system when linked to a thermal water storage vessel, which we would normally always include, means that heat can be stored, removing the peaks and troughs from the demand, and the electricity generated in the most economic way, decoupled from the heat demand.
Q. How many homes would your system heat? What is the impact if the development is mixed used?
A. The Arbor ElectroGen 130kWe as an example, can produce heating and hot water for around 60-100 semi detached homes over the year; but ideally as a mixed use community the supply would follow the demand through the various mixes of uses and therefore the number of dwellings could be reduced. Please contact a LowC specialist for more information.
Q. I only need heat/hot water and use very little electricity – will this still be viable?
A. Yes, we can export surplus electricity to the grid or supply a nearby consumer via a private-wire network.
Q. Can I invest in the technology and let LowC run it for me?
A. Yes, LowC Communities Ltd will take responsibility for the full operation and maintenance of the plant and can provide an ‘evergreen’ warranty. Please ask a LowC specialist for details on the gasifier and engines.
Q. I would prefer to purchase low-cost, low-carbon heat and electricity, and do not want the capital cost of the plant on our company’s balance sheet, can LowC build, own and operate it?
A. Yes, financing is available through LowC. Please ask a LowC specialist for details on the RESCo solution. This is the ideal scenario for County Councils, Local authorities, or National Health/Government bodies who simply wish to sign up for long term security on renewable energy contracts.
LowC Communities Ltd will be happy to engage with all aspects of the Arbor ElectroGen’s planning, design, construction and long-term operation & maintenance – including managing the feedstock.
Q. If LowC build, own and operate the plant, how long is the contract?
A. Typically, LowC Communities Ltd will be happy to develop a contract with the end user for the supply of energy for 15 to 25 years – guaranteeing to provide energy at a price less than an agreed index of a basket of fossil fuels.
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Fuel / Feedstock
Q. What type of biomass does the Arbor ElectroGen use?
A. Any type of wood-based biomass – i.e. arboreal arisings, managed hard or softwoods or processed biomass of an appropriate consistency.
Q. What moisture content does it need to have?
A. The wood can start as a ’green’ wood felled that day as it is dried to the required moisture content during the process. Consequently this can provide land owners with a serious income at minimum process and transportation costs. Equally, it can be dry/seasoned wood providing that it can be formed into the correct size prior to use.
Q. Does the wood have to be processed in some way like the chipping for biomass boilers?
A. Yes, the wood will need to be processed to provide the correct size for feeding into the gasifier. The ideal size is chunks that are comparable to a smartphone/iPhone as this optimises the reaction during gas production without too much dust, and during the drying process allows warm air to pass through effectively.
Q. Can the Arbor ElectroGen system use saw dust, small wood chippings or other biomass products like straw?
A. Yes, the Arbor ElectroGen system can be arranged to accept a number of different feedstock forms where the different constituents and shapes of feedstock have been assessed and predetermined. Typically the processes performance is enhanced by the use of larger feedstock pieces, so where the feedstock originates from smaller matter it can be reformed into larger briquettes before entering the system. Installations intending to use various feedstock types and forms will need to be discussed with a LowC specialist. but only if it’s processed into briquettes and proven to be acceptable for the gasification process.
Q. How much feedstock does the system consume?
A. This depends on the size of the required system capacity, however, the Arbor ElectroGen 500kWe system consumes around 3,400 tonnes of dry feedstock per annum.
Q. How many deliveries will be required?
A. Based on 3,400 dry tonnes per annum that will equate to 340 green wood deliveries in a 20-tonne truck per annum, or approximately 7 visits per week.
Q. Should snow and ice prevent access to site, how much storage capacity does your plant hold?
A. There is storage capacity engineered to suit each application and varies depending on location. As standard we have allowed for storage to suit 7 days of continuous operation.
Q. I’ve heard about problems being caused by feedstock blocking up the feeder systems on biomass systems. What makes yours any different?
A. The Arbor ElectroGen system uses much larger-sized chunks of wood and as such, we’ve developed a purpose-built fuel handling system that avoids the use of small-bore auger technology.
Q. What residual waste / ash is produced?
A. Annually, the plant will produce around 160 tonnes of ash (based on the 500kWe model). The ash largely comprises of unspent charcoal. In the event that the wood fuel is of a known provenance it can be returned directly to the land (nominally 3-5% of the feedstock.)
Q. Is there any commercial value in the ash?
A. Generally yes, along with the oversized and undersized feedstock waste streams, there may be a residual value in the ash. This will be different if the feedstock is not 100% virgin biomass. Please contact a LowC specialist for further information.
Q. If waste/contaminated wood is used as a feedstock, will the Waste Incineration Directive (WID) apply?
A. If non-virgin woods are to be used then an appropriate analysis of the feedstock will determine if the plant should become WID compliant as there are some waste wood materials that are exempt within the WID.
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Emissions
Q. What carbon savings can be made annually?
A. Taking a single Arbor ElectroGen 500 as an example. Annually, it will produce around 4,000 MWh of electricity, 6000 MWh of heat saving a staggering 3,000 tonnes of carbon per annum. These figures are available broken down even further and if your scheme has a target for compliance with either planning consent, or is targeting zero carbon and beyond please contact a LowC specialist for further information.
Q. I have heard that CHP sets running on gas have very low CO2 emissions, how does the Arbor ElectroGen system compare?
A. The CO2 emissions from the whole AE process are almost zero and are 93% lower than producing CHP electricity via natural gas – which is a fossil fuel.
Q. Many biomass boiler schemes in the UK have suffered with complaints from local residents due to particulate discharge from the stack by burning wood and alternative fuels such as straw. How does the AE system compare with this?
A. There are virtually zero particulates discharged to atmosphere from the AE system. This is due to the complete patented combustion process of the fuel and the extended gas cleaning process that is engineered into the system (also patented) making this the perfect solution for built up areas or smoke free urban zones.
Q. Because you are using fuels such as wood I would expect there to be smoke visible from the stack, what is the case here?
A. Once again the system removes all contaminants that would be visible and the plume from the stack under normal atmospheric conditions would be invisible. However when it is very cold the vapour (high temperature water) content of the flue gasses may on occasions produce a visible trace.
Q. Biomass boilers emit a relatively high level of Nitrous oxides (NOx.) Because you are using similar fuels how does the Arbor ElectroGen system compare?
A. Due to the unique combustion process involved, virtually all harmful gaseous emissions are removed during the process, and hence there are virtually no NOx gases emitted by the Arbor ElectroGen system (this is also dramatically lower than those from a natural-gas-fired CHP!).
Q. Apart from particulates and NOx are there other emissions similar to a traditional Biomass (heat only) boiler?
A. No, absolutely not – the emissions from the Arbor ElectroGen system are dramatically lower in all respects due to the fact that the process gas is formed and cleaned in such a unique way that the engine is converting a much cleaner gas to energy.
Q. Naturally a biomass boiler emits a smoke/odour that has could lead to complaints. How does the Arbor ElectroGen system compare?
A. The Arbor ElectroGen system is so clean in its process that there is virtually zero smoke and odour emitted.
Q. What noise is emitted from the plant during operation?
A. The plant is very quiet – the engine is located in an acoustic enclosure as standard. This in turn is located within a building. The complete system is entirely suitable for a location in an urban area and complies with local planning noise regulations.
Q. Biomass boiler wood chippers are generally very noisy. What is the situation if the wood is ‘chipped’ on site?
A. Unlike the traditional heat only biomass boiler, which requires very small pieces of wood to prevent blockages occurring in the auger, the Arbor ElectroGen system uses chunks of wood transported on a conveyor system. This process involves a different type of chipper, which is quieter in operation therefore removing the issues so many operators of biomass boilers suffer from. Please speak to one of the LowC specialists for more information.
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Operation / Maintenance
Q. What’s the plant availability throughout the year?
A. The gasifier plant only needs one week of shutdown every year for planned preventative maintenance. The engines vary however from experience we would normally expect availabilities to be above 8000 hours per year. Naturally if plant redundancy is built into the scheme the overall operating hours could be even higher.
Q. What consumables are required to run the system?
A. A full list of regular consumables can be provided allied to the chosen format and scale of installation.
Q. Is the plant manned 24-hours per day?
A. No, the system is automated and is continuously monitored for performance through the LowC Communities’ data centre. Regular but intermittent visits to ensure that fuel is available to be drawn off are generally all that is needed.
Q. How many people are required to run the system?
A. It will require one person to visit site regularly. This can be part of the LowC service if required.
Q. What if there’s a system failure - do you carry spares in the UK?
A. Critical spare parts would normally be held on site and depending on the level of service contract entered into these would be further supplemented. The full range of spares is carried at strategic locations in the UK to enable us to meet availability guarantees.
For larger scale schemes, at say 5 MW, we would also carry spare engines and alternators at site although this is generally site specific.
Q. How long does the system take to shut down?
A. The gasifier system takes around 72 hours to shut down, which is predominantly the time taken for the internals to cool down.
Q. How long does the system take to start up from cold?
A. The system only takes a few hours to start from cold.
