Installation Guides
This Document serves as a resource for guiding users for feasibility on installing different renewable technologies. This gives enough knowledge to check if it's worth considering a technology before bringing in the relevant installer.
The information on this document is not enough to install anything without professional assistance. Always seek professional, qualified individuals for electrical installations.
Table of contents
Table of contents
Grid Connection vs Island Mode
Exporting to the Grid
Generator Installs
Electrical System
Fuel Tanks
Emissions
Biofuels
Cogenerated Heat and Power (CHP)
Solar Installations
Series and Parallel
Inverters
Mounting Types
Tracking Types
Wind Turbines
Shading Factor
Pole Mounted
Building Mounted
Battery installations
Sizing the Battery
Siting Requirements
Electrical Systems
Heat Sources
Gas Boilers
Ground/Air Source Heat Pumps
Electric Heating
Hot Wells
Grid Connection vs Island Mode
To first understand using Deimos, a quick run through of connecting electrical generators is necessary. Grid connections are common for all commercial applications and understanding of how different equipment connects is useful.
Deimos is designed to take the Grid usage of electricity and gas to model the requirements of a site. Models can be designed for systems using different technologies that can run synched to the grid, isolated from the grid or exporting to the grid.
The diagram above defines the methodology for a changeover system, this has two linked breakers or switched. The system is drawn in 3 phase so there are 3 wires where a domestic single phase system would have 1.
Electricity is taken from Either the grid or the generator, a 1 second gap in supply is present when switching between the grid and a generator. This can be done without consulting a grid operator as the 1 second gap means you do not affect their system, it therefore is far quicker and cheaper to install a system like this however the generation method used needs to fulfil the entire site load at all times otherwise the changeover will flick back to grid.
The diagram above defines how a synchronising system looks, this allows a generator to connect to a live connection from the grid. In the case of an engine, it must be rotating at the same speed and timing as the grid before the synchronising breaker will allow connection.
This system allows for the grid and generator to run in Parallel so the generator can fill in 15% of a load while the grid covers 85%. This gives far more flexibility in a system as the generator can switch on and off without interrupting a site's power supply.
Exporting to the Grid
Synchronised systems also allow for Export which means that you send electricity back to the grid and they pay for it. Depending on your deal with the energy supplier this can be at a constant rate or flexible rate.
Flexible rates can be determined by system imbalance prices. This means you will have a fluctuating pay back from the grid for the energy exported. In the UK this can be a negative price due to excess wind and solar so requires a broker to tell you when to run and when not to. For a helpful site to see these prices right now, check out National Grid: Live .
Generator Installs
Generator installations are a more complex process than other renewable techniques due to the usage of fuel systems, emissions requirements, noise limits and heat rejection.
In the UK the most common and financially viable method is to use a mobile generation unit. This means a genset is in a container or portable canopy which can be transported on a trailer using a HIAB or crane.
Siting a Generator will require enough space for the container of the generator set, if you know what power requirement you have, a quick method is to use a rental company shop by generator power and see the size of container. From that you need a fuel tank nearby and to site it near the mains incomer.
Electrical System
Using the Grid vs Island mode section of this document, decide which works best for yourself. Connection to the grid requires an application to the Distributed Network Operator (DNO) in the UK, 415V is a low voltage installation.
Generator sets are normally 3 phase systems however single phase is an option for smaller sites. 3 phase systems require a set of 5 cables to reach the site breaker L1, L2, L3, Neutral and Earth. The best method is to keep the generator close to the breaker and mains feed as voltage drop over cables means that a large diameter cable is required and can increase costs very quickly.
Site loads can cause issues with generator sets when there are large inductive loads, this could be a motor/pump starting up without a starting system. A professional can check a site for any potential load issues for the generator. This is a major issue when in island mode, grid connections can prevent this from causing failures.
Fuel Tanks
Generators require fuel, depending on consumption different size tanks are required. If a generator is acting as a backup on a site failure, the amount of fuel should be based on the time required for predicted downtimes.
If a generator is being used for consistent generation then defining fuel delivery processes will advise the storage size required. If deliveries are in IBC's of 1000 litres then a tank of at least 1200litres is recommended to allow for a full delivery and some buffer for delivery times. This rule can be scaled up to tanker deliveries of 30,000 litres, in this case, a 40,000litre tank could be recommended.
It is of utmost importance to store fuel safely, this means following COMAH guidance, this can be found in the useful links library. Tanks should be bunded so that a broken tank will not spread fuel in the surrounding area and at least 1.5m from buildings for example.
Emissions
To understand Emissions of generators we first need to define the pollutants from combustion that are controlled by legislations.
- NOx - Nitrogen Oxides are formed in a thermal reaction above 1300°C where Nitrogen reacts with Oxygen.
- HC/PM - Hydrocarbons/Particulate Matter are the result of unburnt fuel, in Diesel this appears as a black smoke. Burning Engine Oil gives white smoke and vegetable oils appears clear/white.
- SOx - Sulphur Oxides are formed when sulphur in fuel reacts with Oxygen from the air and forms an acidic greenhouse gas.
Regulations in the UK and EU are defined within the Medium Plants Combustion Directive (MCPD) and Table 3 gives a value for Engines and Gas Turbines in mg/Nm3.
SOx
120
343
NOx Engines
190
390
PM
10
20
NOx Gas Turbines
200
410
Emissions controls are specified by the installer as it needs to match the exhaust mass flow rate but to give an example of the type of controls required:
- NOx Abatement - Selective Catalytic Reduction (SCR) uses AdBlue to react out the NOx on a catalyst surface at high temperature.
- PM Abatement - Diesel Particulate Filter (DPF) uses a mesh to block large particulates, these then burn off slower in the exhaust stream to smaller components.
- SOx Reduction - Low sulphur fuels are now common in all mainstream suppliers, this is the only effective reduction technique.
Biofuels
Biofuels covers a vast range of fuels, within industrial applications we generally run diesel or gas engines. This document serves to give indication of what the key fuels are and how to decide which is right for a site.
Diesel generators will work well with biodiesels for road transport and potentially any liquid that have calorific values over 36.5MJ/kg and can be similar viscosity to diesel. Fuels in the UK are those specified within the Renewable Transport Fuel Obligation (RTFO) and give Credits (RTFCs) that can be brokered for £0.16 - £0.42 each.
Biodiesels:
- HVO - Hydrogenated Vegetable Oil is a thin, high quality and cost biodiesel which is great for transport applications and can give 2 RTFCs.
- VOME - Vegetable Oil Methyl Esters such as Rapeseed or Soya oil are a good alternative to diesel however are from the food chain and therefore get 1 RTFC.
- UCOME - Used Cooking Oil Methyl Esters are from a waste product and therefore gain 2 RTFCs however can have issues in cold weather.
- FAME - Fatty Acid Methyl Esters are cleaned up waste fats and acid oils gaining 2 RTFCs however have issues in cold weather.
The performance of Methyl Esters tends to be similar to each other as they are broken to a similar type of hydrocarbon, use the UCOME function in Deimos for VOME and FAMEs. HVO runs very differently in engines and trials are recommended to compare.
Alternatives to Biodiesels are low grade fuels that require specific handling to make them run and increase the cost of maintenance on a generator significantly. These can come into issues for waste burning however it is possible to get RTFCs for these as they are waste streams.
Alternatives:
- UCO - Used Cooking Oil in it's raw state can be run with the right mix of handling, generator type and clean up processes.
- Tallow - Animal fats from various animals can be used for generators with the right mix of handling, generator type and clean up processes.
Biofuels can introduce issues with emissions requirements and it is recommended to consult an installer or professional for this purpose to determine what issues you can expect and how to overcome them.
Within Shipping you will see engines running Heavy Fuel Oil (HFO) which is not something we recommend on land unless you are not susceptible to renewable obligations or emissions requirements and have a heavy oil specific generator. Deimos therefore does not model this however if this or any fuel is required on a specific engine, email us at: enquiries@middlegatesoftware.com
Cogenerated Heat and Power (CHP)
CHP is the method of recovering heat from a process that creates heat to be used in another process. Within an engine there is a potential energy within the fuel and depending on the efficiency of the machine, some of this becomes electricity, the majority is heat.
Where fuel is 100% of the input energy, the typical values for outgoing energy show that a CHP system will gain more energy in heat than the electricity produced by the engine.
Solar Installations
Solar Installations are applicable for nearly all situations, solar energy is classified as zero carbon intensity within scope 1 and 2. The carbon equivalent across a solar panel lifetime becomes negative after a few years depending on manufacturer.
Solar is used in many systems to reduce carbon intensity and grid reliance of consumers. The installation of a solar panel is prioritised as grid tied solar panels will provide power to the site and export any excess. If export is not allowed then any excess will be wasted through isolation or as heat.
Deimos models panels as groups in an array pointing the same direction and angle, how they are installed is not important other than inverter efficiencies and mount types. If modelling a large array, 5km2 sections will be modelled with the same solar irradiation data so don't feel the need to define new arrays unless that limit is surpassed.
Series and Parallel
When defining a system design, the initial step is deciding, with your combination of panels, what wiring methodology will be used. This doesn't change the Deimos installation, however will help define the inverters used for efficiency data. Component cost ups are better to be completed by the installer.
Connecting panels in parallel means connecting the negative from adjacent panels to the positive of the next - this makes the voltages add up before the charge controller.
Benefits of installing panels in Series:
- Reduced cable as you can connect between adjacent panels
- Reduced cable diameter as the current is reduced
- Combats losses from temperature drops in high temperature environments that could reduce the voltage below optimal levels for the battery or inverter.
Connecting panels in Series means connecting the grouping the panels together in a connector - this makes the current add up before the charge controller.
Benefits of installing panels in Parallel:
- No high DC voltages makes working with this safer
- You can either use an MPPT controller or a PWM solar controller. Series requires an MPPT controller which is more expensive.
- No need for blocking and bypass diodes as required in series.
- Mixtures of solar panel sizes will function properly and coverage of one panel won't affect others. In series the system bottlenecks to the lower producing panel.
Inverters
Inverters work by changing low voltage DC from Solar Power or batteries into a high voltage AC signal. This can be either single phase for consumer purposes or 3 phase for commercial purposes.
String inverters - For series connected panels and high voltage DC systems. Suffers from reduced performance if one panel in the string does not create as much current.
Grid Tied Inverters - most commonly used in the UK, this means that the solar panels only export energy when they are connected to the grid and there is enough power being produced by the array.
Micro Inverters - For small arrays, this converts to AC at the panel and reduces voltage drops over long distances.
Power Optimisers - An inexpensive alternative for Micro Inverters, work with a String inverter but monitors each panel individually.
Off Grid Inverters - Completely disconnected from the mains, this requires a disconnect from the grid and reconnect to the solar inverter. This works best where the grid is unstable alongside batteries and backup generation.
Hybrid Inverters - When surplus energy is generated, these inverters sell excess to the grid or store in a battery depending on a hierarchy system.
Mounting Types
In Deimos there is an option for building integration, this changes the equation to match panels where there is reduced air flow on the rear of the panel.
Roof mounted panels where there is less than 50cm of air gap between the panel and roof are susceptible to higher temperatures than ground mounted panels. This increased temperature contributes to the thermal degradation above 25°C.
Tracking Types
Deimos allows for several tracking types to be modelled, this is an expensive option however where energy density is required, this can give more power per square meter than static panels.
Wind Turbines
Wind Turbines are a great way to produce power without using any fossil fuels, small scale and industrial wind are modelled in Deimos for land based uses.
When choosing a turbine model, consider the power requirement of the site, wind turbines generate based on a power curve. The rated power is related to the rated speed, different turbines have changing power at different wind speeds, many are constant after hitting the rated speed through to the cut off where the blades will no longer turn.
When considering offshore wind turbines, let us know and we can advise best practice,
Shading Factor
Deimos calculates Land based wind turbines based on forecasting data for 5km2 areas. This gives an idea for the average wind speed in that area, putting a wind turbine in the middle of London however will not give the same results as Deimos as there are too many obstructions in the close proximity.
To give a shading factor, use a 3D assessment of the terrain around the wind turbine. As a general rule of thumb, anything vertically standing off of the ground level, such as a building, from the direction of the wind it will impede 3 times it's height horizontally.
This CFD from a research paper gives an indication of what we can expect in the form of slow wind speeds due to a building, when placing a turbine bear in mind wind will be coming from 360° so wakes are expected in all directions. Take a top down view of all structures that could impede your wind turbine and draw their area of effect to assess shading factor.
Pole Mounted
Free standing wind turbines are the recommended methodology for small through large wind turbines. This methodology allows you to separate the wind turbines from any impeding structures that could reduce the wind energy available.
Building Mounted
A building mounted wind turbine is almost solely for domestic or low energy requirement commercial users. Due to the issue with shading factors
Battery installations
Sizing the Battery
Battery sizing is a complex process as it depends on the usage and intended use. Batteries have 2 main factors to consider when choosing the size
.1Storage Capacity - The amount of energy that can be stored in the battery chemistry
.2Power Output - The amount of energy that can be extracted from the battery chemistry and attached inverter technology
Storage capacity is based on the total energy output however if a manufacturer states that the battery is only rated for 90% DOD (Depth of Discharge) then the battery will be available in Deimos for 90% of it's rating.
Power output is defined as a combination of the battery and it's inverter performance. Most batteries however have a 1 hour discharge time, so have 1kWh storage to each 1kW of output. You can have batteries that store 4x the amount of energy they can output per hour. This could be a 1000kWh / 250 kW battery for example where the inverter is undersized to the battery.
To define the size required, if the battery is for backup uses, the maximum output needs to match the maximum site load and your margin of safety. A data centre would run at 80% of maximum load 99% of the time but need a backup battery rated to 100% of the site load.
If the battery is for assisting alongside a grid backup, then the output can be rated to whatever is expected to be needed. This is where Deimos helps, with half hourly simulations, a battery for overnight energy on a Solar system could be sized to only cover the expected night time usage so the full potential of the battery is used instead of only using the top 40% of the battery.
Siting Requirements
Batteries have an inherent fire risk when installing due to the chemicals used, if you've ever seen a lithium battery fire from piercing a cell then you're aware that thermal runaway can easily cause a fire.
Batteries are installed with controllers that prevent these sorts of failures and the likelihood is rather low within the expected lifetime of the systems.
Electrical Systems
Heat Sources
Gas Boilers
Gas Boilers are familiar in all homes in the UK for converting natural gas into heat, the concept is similar in all sizes industrial and domestic. Defining a coefficient of performance (COP) determines the efficiency of a boiler in converting gas into energy, waste energy is ejected through the exhaust flue.
Gas boilers are a fundamental part of heating systems due to the ease of transporting natural gas down pipelines and the lower price per kWh than electricity. A site with a gas connection is all that is required for smaller installations however larger installations, as imaged above, may require high gas flow connections with a hot room dedicated to the boilers.
Ground/Air Source Heat Pumps
Ground and Air Source heat pumps require electrical energy to create heat however using the refrigeration cycle can gather heat from outside so the amount of electricity is less than the energy produced. This is defined by the Coefficient of Performance (COP). for example a COP of 4 means 1kW of electricity generates 4kW of Heat.
.1Energy is taken from the source of energy - air as low as -15C can be used
.2Energy from the grid used to power the compressor.
.3Evaporator cycle collects energy from outside in refrigerant at low temperature.
.4Expansion Valve reduces the pressure of the refrigerant fluid upstream of the evaporator
.5Condenser provides hot fluid to the heat requirement, in this case a house.
.6Compressor increases the pressure of the refrigerant to the condenser.
Heat pumps can be installed for both domestic and industrial purposes, this allows consumers of hot water or air to create energy in a more efficient manner. This removes requirements for gas and is more efficient than immersion heaters.
Installers will require access to the hot water system and space externally for air source heat pumps. Hot water systems with heat pumps are better as low temperature requirements at 45-50°C to maintain optimum efficiency. The movement from gas to electricity can help with renewable
Electric Heating
Indirect or Direct heating in water using an immersion heater can be used in domestic models or site processes in a factory. Deimos can model these additions using the heat pump model with COP of 1.
Modelled alongside CHP and Hot wells immersion heater usage can be modelled as an addition to replace Gas usage. This is not as efficient as a Heat pump however does not require any external systems in air source or extensive ground work for ground source. The components and following installation becomes less expensive than heat pumps.
Hot Wells
A hot well can be a very simple item that appears even within a domestic house, the intention is to create a storage of heat energy and buffer the requirements from heat sources. Deimos models the heat loss through insulation.
