What input is needed?

Energy sources, trading and export

Modern buildings may act as “prosumers”. They are no longer strictly users of energy that is provided by an outside party, but they may also take an active part in energy trading with utilities as well as with neighbours and even with their own tenants. This requires a common framework, both on a national and an international level, not only for defining certification system requirements, including building codes, but also for evaluating the economic and environmental performance of different system options.

In IDA ICE the environmental accounting is done according to the standard EN ISO 52000-1:2017. Furthermore, IDA ICE provides a framework for economic analysis of buildings and campuses with “next generation” local energy production and conversion. The latter is accomplished by definition of energy Traders in an IDA ICE model, i.e., parties that share a common economic interest, such as facility owners, tenants, neighbours, electric car owners etc.

The assessment boundary

EN ISO 52000-1 «Energy performance of buildings — Overarching EPB assessment — General framework and procedures» considers a physical system in a building, which includes the so called «EPB service», i.e., the part of the building services system that is included in the assessment of the energy performance.

This boundary of the considered physical system, the EPB System, is in ISO 52000-1 called the assessment boundary. The assessment boundary defines the control volume over which the environmental performance of a project is determined. Over the assessment boundary, energy can be delivered into the EPB system or exported out of the EPB system.

Only energy passing the assessment boundary in either direction will impact the total building energy performance as presented in the IDA ICE Delivered Energy Report. This is either when a Trader "inside" the assessment boundary ...

• ... "purchases" energy from a Utility
• ... "buys" energy from another Trader "outside" the assessment boundary
• ... "produces" energy on-site
• ... "exports" energy to a Utility
• ... "sells" energy to another Trader "outside" the assessment boundary
• ... is harnessing "environment" heat or cooling

Energy purchase

If energy from a utility is "purchased" into the assessment boundary, IDA ICE refers to this as “delivered” energy. At present, a Utility is capable of supplying or receiving unlimited energy at any time when needed. Together with the requirement, that everything using energy must have the possibility to receive energy from a utility, this leads to the fact that buildings cannot yet be investigated in the "off-grid" or "island" mode, where energy shortage can happen.

As for all energy that is delevered to the assessment boundary, the environmental weighting factors need to be given for all delivered from Utility energy meters. These factors are:

• Primary energy factor [kWh/kWh]
• Non-renewable primary energy factor [kWh/kWh]
• CO₂ factor [g/kWh]
• Optional national environmental weighting factors

On-site energy production

If renewable energy is generated on site and then "delivered" into the assessment boundary, ISO 52000-1 refers to this as “produced” energy. At present, electrical energy can be produced in two ways in IDA ICE: either by means of photovoltaics or by means of wind turbine(s).

As for all energy that is delevered to the assessment boundary, the environmental weighting factors need to be given for all produced energy meters. These factors are:

• Primary energy factor [kWh/kWh]
• Non-renewable primary energy factor [kWh/kWh]
• CO₂ factor [g/kWh]
• Optional national environmental weighting factors

Energy use

Energy can be used inside or outside the assessment boundary for a specific use (e.g. ideal heaters, heat pumps, chillers, boilers, light, equipment, pumps, fans, etc.). This energy is then consumed and is no longer available.

Energy generation by converters

An energy Carrier is a substance or phenomenon for transferring energy, such as electricity, fuel, or district heat. Energy can be converted from one Carrier to another by special conversion devices, normally called Generators. At present, the only converter in IDA ICE is the combined heat and power generator (CHP) that uses fuel to generate electricity.

Note: At present, a heat pump is not regarded as a conversion device in IDA ICE, but as a consuming device using both electrical energy and environmental heat.

Energy storage

Energy can be stored inside or outside the assessment boundary for later use or sale. At present, the only storage in IDA ICE is the battery that stores electricity.

Energy delivery from outside traders

Someone outside the assessment boundary who owns a device that produces, generates, or stores energy, can sell energy to someone inside the assessment boundary. ISO 52000-1 also refers to this as “delivered” energy.

Energy export

Any energy that leaves the assessment boundary from inside to outside is considered "exported" energy by ISO 52000-1, regardless whether this energy is exported to an energy utility or sold to someone outside the assessment boundary who can directly use or store it.

Energy trading

IDA ICE supports simplified energy trading between parties in the same building/campus/microgrid. These parties, i.e., households, tenants, the main facility owner, electric car owners, etc., are called Traders. A Trader represents a single economic interest. Each Trader will, in turn, have multiple devices that use, produce, generate or store a certain type of energy, e.g., electricity. Each device has one or several Meters, that keep account of the energy flow to and/or from the device. Traders can have Contracts between them, specifying the price at which one of them can buy energy from the other. Every pair of Traders can have up to two Contracts between them, one in each direction.

A special type of Trader is the Utility trader, which represents the economic interest of a utility that is selling energy to or buying energy from the building. If a (non-utility) Trader has a producing device, it must have at least one Contract with a buying Utility Trader. Similarly, it must have a Contract with at least one selling Utility Trader, if it has a device that uses energy. In this context, a storage device (like an electrical battery) is regarded as “using” energy when charged and “producing” energy when discharged. A Trader having a storage device must thus have a Contract with a buying and another Contract with a selling Utility Trader. The same is true for an energy converting device, while here used and generated energy are of different Carriers. A Utility Trader is capable of supplying or receiving unlimited energy when needed at a given price.

An energy Carrier is a substance or phenomenon for transferring energy, such as electricity, fuel, or district heat. In principle, energy trading can be done separately for each Carrier. Heating and cooling energy that has sufficient temperature to be traded is called District heat and District cooling. Thermal energy that does not always fulfil the required conditions for trading, is called Untradeable heat, or Untradeable cooling. However, as at present in IDA ICE there is no generating, storing or producing device for fuel or tradeable thermal energy, interesting trading can in fact only happen with electricity.

IDA ICE provides automatic support in ensuring that Traders trade with each other in a realistic way. However, the actual operation of devices is not involved here. It is assumed that there is some control algorithm that decides when and how much Trader’s devices are operated. This control algorithm may of course, in turn, take prices and trading opportunities into account.

Since no mathematically “correct” trading algorithm exists (real trading depends on subjective decisions by actors with limited knowledge), the presented algorithm attempts to provide realistic and repeatable results without resorting to overly complex assumptions. It follows the principle that every buyer seeks the lowest possible price and every seller seeks the highest possible price. The scope of the energy trading (the local market) is all the Traders that the user decides to describe in the IDA ICE model. I.e., the environmental “assessment boundary” that is the key boundary for the EN ISO 52000-1 study has no relation to the trading process.