GB2575858A

GB2575858A - Balanced energy network

Info

Publication number: GB2575858A
Application number: GB1812191.3A
Authority: GB
Inventors: Hewitt Mark
Original assignee: ICAX Ltd
Current assignee: ICAX Ltd
Priority date: 2018-07-26
Filing date: 2018-07-26
Publication date: 2020-01-29
Anticipated expiration: 2038-07-26
Also published as: GB201812191D0; GB2575858B

Abstract

The balanced energy network system and method combines next generation heat network with smart-grid technology to balance the delivery of heating and electricity in a way that minimizes costs and carbon emissions. The balanced energy network consists of at least two buildings, at least one thermal storage 3, at least one ambient temperature heat network or Cold Water Heat Network (CWHN) 1, heat pumps 2, smart hot water storage 5 and demand side response (DSR) service 4. The system operates by a controller monitoring and controlling the water flow temperature in a pipe network carrying water at ground temperature wherein the water is obtained from one or more of the at least one heat pump, the at least one thermal storage and the at least one smart hot water storage. The controller receives requests from the demand side response system to adjust power draw and quantify the capacity of the balanced energy network to determine whether to accept requests and thereby control the heat pump. The thermal storage may be open loop and comprise boreholes, an aquifer, river, sea or air.

Description

Balanced Energy Network

Field of the Invention

The present invention relates generally to energy networks and more particularly to providing a balanced energy network, that is a system for delivering heating and cooling energy to buildings and responding to demand side management (DSM) calls for turning up or turning down grid electrical load.

Background of the Invention

The following discussion of the prior art is intended to facilitate an understanding of the invention and to enable the advantages of it to be more fully understood. It should be appreciated, however, that any reference to prior art throughout the specification should not be construed as an express or implied admission that such prior art is widely known or forms part of common general knowledge in the field.

Current district heating systems are expensive, and require long lead times, and commitment from large users before they are viable. It is difficult and often expensive to opt in and out of existing district heating systems.

Furthermore, current district heating systems are generally powered by gas or gas CHP (Combined Heat and Power) units, which are large emitters of carbon dioxide (chemical formula CO₂) and other problematic pollutants, such as particulates and nitrogen dioxide (chemical formula NO₂).

Current aquifer thermal energy systems (ATES) are not enabled for demand side management (DSM).

Current geothermal heat pump or ground source heat pump (GSHP) systems are not designed to output at temperatures which meet mainstream existing heating flow and return temperature requirements, and therefore are not suitable for mass retrofitting of existing buildings and networks.

It is an object of the present invention to overcome or substantially ameliorate one or more of the deficiencies of the prior art, or at least to provide a useful alternative.

Summary of the Invention

Accordingly, the invention provides a balanced energy network as defined in the independent claims.

Alternatively, a balanced energy network (BEN) can be called a cold water heat network (CWHN). The system is intended to allow buildings and groups of buildings to be efficiently heated and cooled, and to assist in grid balancing.

A BEN has the ability to control multi-vector energy efficiencies. This means that the BEN is capable of using all parts of the system to create energy efficiencies and allows demand side management (DSM) of BEN linked devices.

The BEN controller ensures that all customer buildings are receiving the optimal (low temperature) flow temperatures in the BEN circuit, and that customer buildings can be provided with flow temperatures which allow for heating and cooling simultaneously in each individual building, and across the network. Because the pipe network providing the water only needs to carry low temperature water, the pipes do not need to be heavily insulated. A light insulation is sufficient. Also, since heating and cooling is provided by the same circuit, the same water can be used for heating and cooling, therefore fewer pipes are required.

The BEN controller enables heat pump devices to be available for demand side management (DSM). This means that the heat pumps are able to respond to requests from an aggregator (an organisation that mediates between consumers and suppliers of electricity) to turn up or down electrical power draw in response to grid demands, balanced against user needs. The BEN controller is able to quantify the capacity of the system to accept aggregator demands for turn up or down. Demand side management is set to play a major role in national electrical grid balancing, e.g. in the UK.

The infrastructure cost of a BEN is much lower than conventional high temperature district heating systems. It is much easier to arrange for building customers to opt in or out of a BEN than a conventional district heating system.

The heat pumps developed for the BEN system are capable of delivering at temperatures that match the requirements of mainstream existing heating systems (up to 80 degrees Celsius).

The BEN system is callable of taking waste heat from industrial or ambient sources, including electrical gear, process waste heat from plant, and heat recovery from sources such as sewerage.

The BEN system does not produce CO₂ or other pollutants (such as NO₂) on site.

Brief Description of the Drawings

Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is an exemplary sketch of a balanced energy network system.

Figure 2 is a flowchart of a method for balancing the delivery of heating and electricity.

Detailed Description

The present invention provides a balanced energy network for delivering heating and cooling energy to buildings. It can also respond to demand side management (DSM) calls for turning up or turning down grid electrical load.

A BEN is a heat pump driven network that uses a low temperature heat network to link buildings together, and makes use of demand side response to communicate with the national grid and use electricity at optimal times. This essentially turns the heat pumps and the buildings themselves into distributed storage systems that provide a low cost balancing service for the national grid.

The BEN system combines next generation heat network with smart-grid technology to balance the delivery of heating and electricity in a way that minimizes costs and carbon emissions. BEN consists of borehole thermal storage, an ambient temperature heat network, heat pumps, smart hot water storage and demand side response (DSR) service. A novel energy performance index - total system efficiency (TSE), considering heat pump and hot water tank, is used for measuring the efficiency of the BEN. It can be demonstrated by simulation analysis that the effective coefficient of performance (COP) varies from 1.8 to 2.5 in one of the coldest months of the year, which greatly improves on the energy efficiency over existing technologies. Following that, diverse effects of heat pump COP, borehole and heat pump output temperature, effective COP on energy performance and costs have been investigated. Simulation results show that the used high temperature heat pumps in BEN operate at expectedly higher COP, which fluctuated between 3.1 and 3.2 with Carnot efficiency at 0.5. The optimal operating output temperature of heat pump in BEN is around 70 degrees Celsius.

The basic principle behind BEN is to electrify heat while minimizing the impact to peak grid electrical loads using a novel combination of measures.

An exemplary setup is described in the following. The values are not essential to the invention and are merely indicated to allow a better understanding of the example.

In this example, a BEN could link two buildings with two boreholes that deliver groundwater from the aquifer. The boreholes operate as heat sinks or thermal storages, through which the circuit water temperature is brought in to balance by taking heat from or rejecting it to the boreholes. Alternatively, instead of the boreholes, other heat sinks could be used, for example an aquifer, a river, the sea or the air). The water could, for example, be initially at a temperature of around 13 to 15 degrees Celsius and a flow rate of 20 litres per second. This open loop borehole system provides the heat sink source for the heat pumps, conveyed by the cold water network (CWHN). The temperature in the CWHN can be raised by heat rejection, which would in turn improve the COP of heat pumps in heating mode. Overall system performance can also be improved by shifting loads to off-peak times through a combination of distributed thermal storage and demand side response (DSR). While these technologies have all been proven individually, BEN is the first known heat network to integrate them all into a balanced system.

The first step in the BEN model is to operate the boreholes and pump the cold water that carries and distributes thermal energy throughout the network. They are essentially constant water sources. Heat loss through the borehole’s lining into the ground is simulated and electricity is consumed based on the volume of water pumped. Electricity consumption of the borehole pump is also recorded. Inside temperature of borehole T_billi+i in i+1 step is calculated as follows:

γι __ γι __ rtfrorVrtfr_or0.001/Cj/J Z ™ __ γ, X , . .

^lbin_i+1 - ibint V_TC_H20M \^lbint ‘ambJU)

The pipework is simulated similarly to the borehole by what is commonly referred to as the “node” method. The pipes are “segmented” into discrete sections then, temperatures and heat losses are calculated for each segment down the pipe. The pipe’s internal temperature Tpini+i in i+1 step is defined by _{T T} A_pipVU_pip0.001kJ/J _r ^ινίηΐ₊₁ ^ιρίηι VrC^M ^{1 amb}

V_TC_H20M

As mentioned before, the heat pumps were modelled as standard Carnot heat pumps with a 0.5 scaling factor applied to the COP. Heat pump COP is determined from the temperature of the condenser/evaporator water loops. The flow rate is adjusted to the heat available. The heat available is in turn determined by the temperature of the water from the boreholes. Then heat is pumped from the cool water to temperature reaches 70 °C.

the warm water until the warm water

QQP _ Twq+273

Two^-Teo * ε (3)

The smart hot water tanks, alternative water tanks are possible too, simulated by calculating weighted averages of the water in the tank and the water flowing into it. The 15-minute time steps are then divided in the hot water tank simulations into 1-minute long “sub-time steps” to further improve accuracy. At each time step the water temperature is averaged as water flows in and out. Finally, heat losses are calculated. Immersion heaters supplied by electricity in the hot water tanks maintain the water temperature once the COP of the heat pumps drops below 2. This water is then sent to the buildings at around 70 °C to supply the heat emitters (primarily conventional radiators).

The buildings are simulated as thermal stores. Fabric heat losses Q_fab and ventilation heat losses Qvent are calculated at each time step and determined by equations 3 and 4, respectively.

_ ^Bldg(Tin Tbldgt /^\ Vfab — 3600k]/kWh ' '

Q_heat is the thermal energy that is needed to heat the building temperature to the desired temperature and calculated by equation 5.

q _ VeidgiTin TAmb}tAch.C_ai_rp_ai_r

X.vent '

3600kJ/kWh

Q_tot is the total thermal energy required to heat the buildings and is defined by equation 6.

Qheat ~ MtheriTdes Tj_n) (6)

Furthermore, the required heat to maintain the desired building temperature T_des is extracted from the water pumped through it by equation 7.

Qtot ~ Qfab T Qvent T Qheat (7)

The flow temperature into buildings T_b|_dgin and out of buildings T_b|_dgout are defined by equations 8 and 9, respectively.

_T _ _T Ptot*3600^kJ/_kwh lbldg_i+1 ~ Ibldgt I ) (°) ’ — T__^Qtot (Q\ bldgout — ¹ bldgin y_TtC^ p

This water then repeats its journey through the warm cycle once again by flowing to the heat pumps to be reheated.

The building construction material for the buildings is assumed to be primarily concrete which has a specific heat of 0.84 kJ/(kg K) and density of 2100 kg/m³. Building thermal masses were then calculated using the building concrete volume V_con and the specific heat of concrete C_con. With these parameters the building thermal masses M_ther were calculated by

Mther ~ ^conPcon^con (1θ)

Turning now to Figure 1, the BEN 1 (cold water heat network) comprises heat pumps 2, borehole thermal storage 3, demand side response 4, smart hot water storage 5. The BEN is also attached to some sort of source of electricity 6, which favourably is of the type low/zero carbon (as shown) and is optionally linked to other networks 7.

Heat pumps 2, also called ambient temperature CWHN, are used to share heat between the buildings. Therewith water is circulated at a temperature of approximately 13°C. CWHN enables buildings to be connected hydraulically enabling heat to be abstracted when a building requires heating or rejected to when a building requires cooling.

If a current system is fitted to the new BEN, the buildings are previously served by a series of gas fired boilers operating in a cascade system. So, the underlying source of energy for heating can be shifted from gas to electricity and the most efficient combination to match the building needs will be required. The BEN links heat pumps into this cascade system, which requires matching the distribution temperatures for the common header. High temperature heat pumps deliver these higher output temperatures efficiently.

If the buildings linked to the CWHN loop had perfectly balanced heating and cooling loads it would be possible to use the rejected heat from one building to supply much of the source heat for another. In practice, both the buildings are often heating dominated buildings that will be removing heat from the CWHN for much of the year. In order to maintain the 13°C circulating network temperature, the CWHN is linked to an open loop borehole thermal storage system 3. The geothermal boreholes can for example be 110 m deep each, reaching the chalk aquifer beneath the surface and delivering water, for example at a rate of 20 l/s.

A DSR 4 can typically link to distributed storage assets such as batteries and stand-by generators. With this invention heat pumps and industrial sized storage cylinders can be managed. By linking DSR control systems directly into the heat network itself this distributed storage capacity can be expanded. A BEN uses dynamic price signals to turn the heat pumps and cylinder storage systems on and off at optimal times, generating DSR revenue as well as limiting the impact of the electrified heat at peak times. The electrical infrastructure challenges of adjusting both the national grid to cope with intermittent renewable generation and massive electrification and local electricity networks to allow widespread introduction of heat pumps into buildings are significant.

The BEN system incorporates smart hot water cylinders 5. In the example 2 cylinders each having a capacity of 10,000 litres are used. With the smart hot water cylinders the storage resources available for DSR flexibility are enhanced. The cylinders can be charged either from the heat pumps or via direct electric immersion heaters.

While the BEN system can be linked to any source of energy 6, low and zero carbon electricity generation devices and waste heat sources are strongly preferred. The BEN system can provide a local platform to integrate the resource with minimal distribution losses, and distributed storage options can provide a buffer against intermittency.

More than two buildings can be connected. Either in any number which is desired individually, but also in sets of buildings. So, for example, a new building can be integrated into a group of buildings that are using a BEN already, but also two groups can be joined together. Such a connection can be effected for example through the CWHN pipes by adding both cooling and heating demand with a view to improving the balance of the network overall and also via a cloud system to take advantage of the DSR.

The ultimate objective of the BEN project is to form a smart energy heat sharing network system by which low carbon and relatively inexpensive heating and cooling is produced and can grow organically across cities and towns.

A balanced energy network as presented herein, brings together cross-sector supply chains to deliver integrated energy solutions at different scales to meet the energy systems challenges of achieving a low-carbon economy: secure, affordable, sustainable energy.

The network efficiently uses renewable energy based on the recycling of solar heat (from the summer) to thermal energy storage in the ground through the autumn, to the time of need for heat (in winter).

Heat pumps are used to transfer heat to buildings in winter instead of generating heat afresh when needed by burning fossil fuels. The heat pumps can deliver high temperatures so that they can be retrofitted into existing buildings in place of gas boilers and use existing heat distributions systems directly.

Heat is recovered from buildings needing cooling and transferred to those needing heating and domestic hot water on a heat sharing network.

Balancing the supply and demand for heat through the seasons is mirrored by balancing the supply and demand for electric power by shifting some of the demand from times of peak consumption (by day) to times of excess supply (by night).

Unless specifically stated otherwise, as apparent from the following discussions, it is appreciated that throughout the specification discussions utilizing terms such as processing, computing, calculating, determining, analysing or the like, refer to the action and I or processes of a computer or computing system, or similar electronic computing component, that manipulate and I or transform data represented as physical, such as electronic, quantities into other data similarly represented as physical quantities.

It will be understood that the steps of methods discussed are performed in one embodiment by an appropriate processor (or processors) of a processing (i.e., computer) system executing instructions (computer-readable code) stored in storage. It will also be understood that the invention is not limited to any particular implementation or programming technique and that the invention may be implemented using any appropriate techniques for implementing the functionality described herein. The invention is not limited to any particular programming language or operating system.

Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases in one embodiment or in an embodiment in various places 10 throughout this specification are not necessarily all referring to the same embodiment but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those skilled in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

Claims

1. A balanced energy network system, which is configured to balance the delivery of heating and electricity to at least two buildings, comprising:

a controller, at least one heat pump (2), at least one thermal storage (3), a demand side response system (4), at least one smart hot water storage (5), at least one energy source (6), and a pipe network carrying water at ground temperature, the pipe network connecting the at least one heat pump, the at least two buildings, the at least one thermal storage, and the at least one hot water storage, wherein the controller is configured to monitor the water flow temperature in the pipe network, to control the water flow temperatures in the pipe network for each of the at least two buildings, wherein the water is obtained from one or more of the at least one heat pump, the at least one thermal storage and the at least one smart hot water storage, to receive requests from the demand side response system to turn up or down electrical power draw from the at least one energy source of the at least one heat pump, wherein the requests are based on grid demands and balanced against user needs, to quantify the capacity of the balanced energy network system to determine whether to accept the requests, and to control the at least one heat pump to turn up or down electrical power draw based on the requests, and wherein the at least heat pump is capable to deliver a temperature of up to 80 degrees Celsius.

2. A balanced energy network system according to claim 1, wherein the system is configured to integrate waste heat from industrial or ambient sources, including electrical gear, process waste heat from plant, or heat recovery from sources such as sewerage.

3. A balanced energy network system according to one of claims 1 to 2, wherein the at least one thermal storage is one or more of boreholes, an aquifer, a river, the sea or the air.

4. A balanced energy network system according to one of claims 1 to 3, wherein the system is configured to be connected to another balanced energy network system or another building.

5. A balanced energy network system according to one of claims 1 to 4, wherein the at least one energy source is preferably of low or zero carbon type.

6. A method (100) for balancing the delivery of heating and electricity to at least two buildings within a balanced energy network system, the method being performed by a controller of the balanced energy network system, the method comprising the steps:

monitoring (110) the water flow temperature in a pipe network carrying water at ground temperature, the pipe network connecting at least one heat pump, the at least two buildings, at least one thermal storage, and at least one hot water storage, wherein the at least heat pump is capable of delivering a temperature of up to 80 degrees Celsius, controlling (120) the water flow temperatures in the pipe network for each of the at least two buildings, wherein the water is obtained from one or more of the at least one heat pump, the at least one thermal storage and the at least one smart hot water storage, receiving (130) requests from a demand side response system to turn up or down electrical power draw from at least one energy source of the at least one heat pump, wherein the requests are based on grid demands and balanced against user needs, quantifying (140) the capacity of the balanced energy network system to determine whether to accept the requests, and controlling (150) the at least one heat pump to turn up or down electrical power draw based on the requests.

7. A method according to claim 6, wherein the controlling step (120) comprises integrating (125) waste heat from industrial or ambient sources, including electrical gear, process waste heat from plant, or heat recovery from sources such as sewerage.

8. A method according to one of claims 6 to 7, wherein the at least one thermal storage is one or more of boreholes, an aquifer, a river, the sea or the air.

9. A method according to one of claims 6 to 8, wherein the method is performed for at least two connected balanced energy network systems or a balanced energy network system connected to another building.

5

10. A method according to one of claims 6 to 9, wherein the at least one energy source is preferably of low or zero carbon type.