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Authors:
email:
Date:
Version:
Fabian Mueller
Olle Sundstroem
Dieter Gantenbein
{fmu,osu,dga}@zurich.ibm.com
19.03.2014
2.1
Subject:
IBM EcoGrid Direct-Price Agent Implementation Status
1
1
Scope
This document introduces an updated version of the IBM EcoGrid Direct-Price Agent v2 as described
in [1].
The functional principle of the updated direct-price agent, hereafter referred to as version 2.1, is the same as
in version 2.0. However, the heat pump runtime constraints have been changed for the different flexibility
levels so as to allow for more potential for demand response.
2
Heat Pump Operational Constraints
The heat pump runtime constraints we had implemented in the previous version 2.0 of the direct-price agent
are summarized in Table 1.
User-set
Aggressivity Level
Low
Medium
High
Min. Off-time
Max. Off-time
Min. On-time
15min
15min
15min
15min
30min
60min
120min
60min
30min
Max. total Offtime per day
15min
30min
60min
Table 1 Heat pump operational constraints for different user settings as implemented in previous price agent version 2.0.
The updated runtime constraints used in the new price agent version 2.1 are provided in Table 2. Note that in
new version, the maximum cumulative daily off-time constraints are removed. Moreover, both the minimum
and maximum off-times have been increased. Consequently, the heat pump and direct electric heating is now
allowed to be throttled for time periods that are longer.
To summarize the new v2.1 behavior, note that, regardless of the user-set flexibility level, the time
between the start times of two subsequent heat pump off-periods is guaranteed to be at least 4 hours
(=240min).
User-set
Aggressivity Level
Low
Medium
High
Min. Off-time
Max. Off-time
Min. On-time
30min
30min
60min
30min
60min
90min
210min
210min
180min
Max. total Offtime per day
-
Table 2 Heat pump operational constraints for different user settings as implemented in the price agent version 2.1.
3
Heat Pump Model
The version of the direct-price agent described in this document uses a very simple heat pump
model. It is assumed that the heat pump consumes a constant amount of power PON when in
operation, and a constant amount of power POFF when idle.
The numeric power level values can be identified for every house individually. Table 3 provides a
set of typical values.
2
Heat Pump Operation
State
ON
OFF
Constant Power
Consumption
4000W
130W
Table 3 Example of heat pump power levels.
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Energy-Procurement Cost Minimization
Given a price forecast for a fixed planning horizon, the IBM direct-price agent computes a heat
pump ON/OFF schedule that (i) minimizes the total energy-procurement cost accumulated over the
planning horizon and that (ii) simultaneously satisfies all runtime constraints as specified in Table
2.
5
Security Features
In addition to the heat pump constraints discussed in Section 2, the following security features are
implemented to guarantee participant freedom and an indoor air temperature higher or equal to the
user-set minimum temperature at all times.
As soon as at least one of the following conditions is true, any planned minimum procurement-cost
optimization schedule will be pre-empted and the heat pump is unconditionally enabled to operate
according to its native parameters.
i.
ii.
iii.
iv.
v.
vi.
The indoor air temperature as measured by the GreenWave temperature sensor is below the
user-set minimum temperature.
The indoor air temperature is below minimum User Comfort Setting established in UI.
The latest indoor air temperature sample from the GreenWave temperature sensor was
received more than 4 hours ago.
The communication between server and GreenWave gateway in house is lost for more than
30 minutes.
Oestkraft or the participant operationally bail out the household from automation by
unchecking the flag in GreenWave user interface.
The IBM administrative automation state for the household is set to disabled (example as
done over Xmas 13/14).
References
[1]
Mueller, F., Sundstroem, O., & Gantenbein, D. (2014). IBM EcoGrid Direct-Price Agent
Implementation Status v2.0. IBM Research Zurich.
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